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Federal voting rights in Puerto Rico
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Voting rights of United States citizens in Puerto Rico, like the voting rights of residents of other United States territories, differ from those of United States citizens in each of the fifty states and the District of Columbia. Residents of Puerto Rico and other U.S. territories do not have voting representation in the United States Congress, and are not entitled to electoral votes for President. The United States Constitution grants congressional voting representation to U.S. states, which Puerto Rico and other U.S. territories are not, specifying that members of Congress shall be elected by direct popular vote and that the President and the Vice President shall be elected by electors chosen by the States.[Note 1]
Puerto Rico is a territory under the sovereignty of the federal government, but is not part of any state nor is it a state itself. It has been organized (given a measure of self-rule by the Congress) subject to the Congress' plenary powers under the territorial clause of Article IV, sec. 3, of the U.S. Constitution.[1] In the U.S. House of Representatives, Puerto Rico is entitled to a Resident Commissioner, a delegate who is not allowed to vote on the floor of the House, but can vote on procedural matters and in House committees. In most other U.S. overseas (and historically pre-state) territories, as well as the District of Columbia, a similar representative position is styled Delegate.
The lack of direct voting representation in Congress for residents of the territory has been an issue since the U.S. Congress granted U.S. citizenship to Puerto Rico citizens in 1917. All judicial claims have been met with political or constitutional challenges; therefore, there has been no change in Puerto Rico's representation in the Congress or representation on the electoral college for the U.S. citizens residing in Puerto Rico.
Like other territories, Puerto Rico can participate in the presidential primary process. It holds a primary election in the spring of each presidential election year. Then the parties choose delegates to the Republican and Democratic National Convention, who are pledged to vote at that convention for the winners of Puerto Rico's primary, but that's the end of their participation in the presidential election. See United States presidential primaries in Puerto Rico, 2016.
Contents
[hide]
1 Background
2 Inter-American Commission on Human Rights claim
3 Disenfranchisement in Puerto Rico
4 Igartúa v. U.S
5 See also
6 Notes
7 References
Background[edit]
Puerto Rico is an insular area—a United States territory that is neither a part of one of the fifty states nor a part of the District of Columbia, the nation's federal district. Insular areas, including Puerto Rico, the U.S. Virgin Islands and Guam, are not allowed to choose electors in U.S. presidential elections or elect voting members of the U.S. Congress. This grows out of Articles One and Two of the United States Constitution, which state that electors are to be chosen by "the People of the several States." In 1961, the 23rd amendment extended the right to choose electors to the District of Columbia; the insular areas, however, were not addressed in that Amendment.
Inter-American Commission on Human Rights claim[edit]
On December 29, 2003, The Inter-American Commission on Human Rights of the Organization of American States concluded that the United States is responsible for violations of the District of Columbia's rights under Articles II and XX of the American Declaration of the Rights and Duties of Man by denying District of Columbia citizens an effective opportunity to participate in their federal legislature.[2] On October 17, 2006, Pedro Rosselló, a former governor of Puerto Rico, and the Unfinished Business of American Democracy Committee on behalf of the approximately four million U.S. citizens residing in the Commonwealth of Puerto Rico, presented a petition to the Inter-American Commission on Human Rights of the Organization of American States seeking the Commission's aid in obtaining enfranchisement.[3]
Disenfranchisement in Puerto Rico[edit]
Further information: Voting rights in the United States § Overseas and nonresident citizens
Any U.S. citizen who resides in Puerto Rico is effectively disenfranchised at the national level, as are all U.S. citizen residents of U.S. unincorporated territories.[4] Although the Republican Party and Democratic Party chapters in Puerto Rico have selected voting delegates to the national nominating conventions participating on U.S. presidential primaries or caucuses, U.S. citizens without a voting residence in one of the 50 states or in the District of Columbia may not vote in federal elections.[5]
Both the Puerto Rican Independence Party and the New Progressive Party outright reject[citation needed] the status quo that permits disenfranchisement (from their distinct respective positions on the ideal enfranchised status for the island-nation of Puerto Rico). The remaining political organization, the Popular Democratic Party, is less active in its opposition[citation needed][according to whom?] of this case of disenfranchisement but has officially stated that it favors fixing the remaining "deficits of democracy" that the Bill Clinton and George W. Bush administrations have publicly recognized in writing through reports of the President's Task Force on Puerto Rico's Status.[6][7]
Various scholars[who?], including a US judge in the United States Court of Appeals for the First Circuit,[citation needed] conclude that the U.S. national-electoral process is not fully democratic due to U.S. government disenfranchisement of U.S. citizens residing in Puerto Rico.[8][9]
The appeals court decision in 2005, on appeal of the decision in the third filing of the case Igartua-de la Rosa v. United States, 417 F.3d 145 (1st Cir. P.R. 2005), reads in part:[10]
August 3, 2005
OPINION EN BANC
Boudin, Chief Judge. This case brings before this court the third in a series of law suits by Gregorio Igartúa, a U.S. citizen resident in Puerto Rico, claiming the constitutional right to vote quadrennially for President and Vice President of the United States. Panels of this court have rejected such claims on all three occasions. We now do so again, this time en banc, rejecting as well an adjacent claim: that the failure of the Constitution to grant this vote should be declared a violation of U.S. treaty obligations.
The constitutional claim is readily answered. Voting for President and Vice President of the United States is governed neither by rhetoric nor intuitive values but by a provision of the Constitution. This provision does not confer the franchise on "U.S. citizens" but on "Electors" who are to be "appoint[ed]" by each "State," in "such Manner" as the state legislature may direct, equal to the number of Senators and Representatives to whom the state is entitled. U.S. Const. art. II, § 1, cl. 2; see also id. amend. XII.
Judges Campbell and Lipez concurred in the decision. Judge Torruella dissented, opening his dissent as follows:[10]
In its haste to "put [plaintiffs-appellants'] constitutional claim fully at rest," maj. op. at 6, the majority has chosen to overlook the issues actually before this en banc court as framed by the order of the rehearing panel, see Igartúa de la Rosa v. United States, 404 F.3d 1 (1st Cir. 2005) (order granting panel rehearing), which panel the en banc court suppressed, but whose order was adopted as establishing the parameters of the issues to be decided by the en banc court. See Igartúa de la Rosa v. United States, 407 F.3d 30, 31 (1st Cir. 2005) (converting to en banc review panel rehearing in which "the parties [are] to address two issues: first, the plaintiffs' claim that the United States was in default of its treaty obligations and, second, the availability of declaratory judgment concerning the government's compliance with any such obligations."). It is these issues that the parties were asked to brief. Instead the majority has sidetracked this appeal into a dead end that is no longer before us: Puerto Rico's lack of electoral college representation, see U.S. Const. art. II, § 1, cl. 2, and our lack of authority to order any constitutional change to such status by reason of that constitutional impediment.
In doing so, the majority fails to give any weight to the fundamental nature of the right to vote, and the legal consequences of this cardinal principal. Under the combined guise of alleged political question doctrine, its admitted desire to avoid "embarrassment" to the United States, and its pious lecturing on what it deems to be the nature of the judicial function, the majority seeks to avoid what I believe is its paramount duty over and above these stated goals: to do justice to the civil rights of the four million United States citizens who reside in Puerto Rico. The majority labels this duty with despect as "rhetoric" and "intuitive values." Maj. op. at 3. I beg to differ, and so, I suspect, do a considerable number of those four million U.S. citizens who, lacking any political recourse, look to the courts of the United States for succor because they are without any other avenue of relief. See United States v. Carolene Prods. Co., 304 U.S. 144, 152 n.4 (1938) ("[P]rejudice against discrete and insular minorities may be a special condition, which tends seriously to curtail the operation of those political processes ordinarily to be relied upon to protect minorities and . . . may call for correspondingly more searching judicial inquiry.").
Igartúa v. U.S[edit]
On November 24, 2010, Gregorio Igartúa and others brought suit claiming they and other U.S. citizen-residents of Puerto Rico have a right to vote for a Representative to the U.S. House of Representatives from Puerto Rico and a right to have Representatives from Puerto Rico in that body. In 1917, residents of Puerto Rico were granted U.S. citizenship by statute. See Pub.L. No. 368, ch. 145, § 5, 39 Stat. 951 (1917).
The panel is unanimous in agreeing that the U.S. Constitution does not give Puerto Rico residents the right to vote for members of the House of Representatives because Puerto Rico is not a state.
Chief Judge Lynch and Judge Lipez conclude that this panel is bound by Igartúa III's holding that the Constitution does not permit granting such a right to the plaintiffs by means other than those specified for achieving statehood or by amendment. Chief Judge Lynch independently concludes that this holding in Igartúa III is correct. Judge Lipez considers the panel bound by this holding in Igartúa III, but he does not express a view of his own on its merit. Chief Judge Lynch and Judge Lipez agree that Igartúa III requires dismissal of plaintiffs' claims based on treaties and international law. Judge Lipez joins the holding that dismissal of the case is affirmed. He joins this introduction, the introduction to Section II, Sections II.A, II.B, and II.C.1, and Section III of Chief Judge Lynch's opinion. He expresses additional views in his concurring opinion.
Judge Torruella dissents and is of the view that the constitutional text neither denies citizens of Puerto Rico the right to vote for members of the House of Representatives nor imposes a limitation on the federal government's authority to extend the franchise to territorial residents under other constitutional powers.
Lipez opened his concurrence opinion as follows:[11]
-Concurring Opinion Follows-
LIPEZ, Circuit Judge, concurring in the judgment. Despite our court's 2005 en banc decision rejecting the right of Puerto Rico's four million residents to vote in presidential elections, the issue of federal voting rights for these longstanding United States citizens remains a compelling legal problem. The unequal distribution of the fundamental privilege of voting among different categories of citizens is deeply troubling and, not surprisingly, the legal arguments in favor of enfranchising Puerto Rico residents have continued to evolve. Although the en banc decision forecloses this panel's reconsideration of issues the full court resolved, that decision should not be the final word on the subject. Judge Torruella's dissent highlights important issues that deserve consideration in a new en banc proceeding. As I shall explain, if each of those issues were decided in plaintiffs' favor, United States citizens residing in Puerto Rico would have a viable claim to equal voting rights under the International Covenant on Civil and Political Rights ("ICCPR").
Thus, while I agree with Chief Judge Lynch that our panel must adhere to the precedent set five years ago by the en banc court on the constitutional and treaty interpretation issues addressed in the majority opinion, I cannot agree that the plaintiffs' claims should be dismissed without review by the full court. Given the magnitude of the issues and Judge Torruella's forceful analysis, this is one of those rare occasions when reconsideration of an en banc ruling is warranted.
Lipez, on his concurrence opinion on a section of The Constitutional Argument indicated:[11]
-Concurring Opinion Follows-
As Judge Torruella points out, the view that the Constitution does not necessarily forbid extensions of the rights it delineates has been articulated in scholarly writing, and it underlies the effort to legislate voting rights for residents of the District of Columbia. See Opinion of Torruella, J.; see also José R. Coleman Tió, Comment, Six Puerto Rican Congressmen Go to Washington, 116 Yale L.J. 1389, 1394 (2007). Judge Torruella aptly invokes as well precedent applying the same notion of the Constitution's reach-i.e., that it neither requires nor prohibits conferring rights on citizens outside the States-in the context of diversity jurisdiction. That precedent, including the Supreme Court's decision in National Mutual Insurance Co. v. Tidewater Transfer Co., 337 U.S. 582 (1949), confirmed Congress's power to extend diversity jurisdiction to the District of Columbia even though the provisions of Article III creating such jurisdiction refer only to States. By analogy, such cases support the argument that references in Article I to the voting rights of the people of "the States" are not necessarily negative references to the voting rights of citizens residing in other United States jurisdictions. Cf. Adams v. Clinton, 90 F.Supp.2d 35, 95 (D.D.C.2000) (Oberdorfer, J., dissenting in part) ("[T]he use of the term ‘State’ in the diversity jurisdiction clause of the Constitution cannot mean ‘and not of the District of Columbia.’ " (citing Tidewater )).
Moreover, the redressability concern that underlay my concurrence in Igartúa III stemmed in large part from the courts' inability to order Congress to take the only actions that I thought could deliver the remedy the plaintiffs sought-"to either admit Puerto Rico as a state or to propose a Constitutional amendment allocating electors to Puerto Rico." See 417 F.3d at 154. If Puerto Rico residents' right to vote originates from a source of United States law other than the Constitution, however, it is possible that declaratory relief could properly involve individual government officials rather than Congress. For example, precedent indicates that the Secretary of Commerce is empowered to take the steps necessary to conform the apportionment process to the law. See Franklin v. Massachusetts, 505 U.S. 788, 802 (1992) (plurality opinion) (noting that "injunctive relief against executive officials like the Secretary of Commerce is within the courts' power") (citing Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952)); Adams, 90 F.Supp.2d at 41 (noting that the Secretary of Commerce is tasked with reporting the population of each state to the President for congressional apportionment).
Torruella opened his Opinion Concurring in Part and Dissenting in Part, as follows:[11]
TORRUELLA, Circuit Judge (Concurring in part; Dissenting in part). Although in a different format than presented on prior occasions, we once more have before us issues that arise by reason of the political inequality that exists within the body politic of the United States, as regards the four million citizens of this Nation who reside in Puerto Rico.
This is a fundamental constitutional question that will not go away notwithstanding this Court's repeated efforts to suppress these issues.21 We can now add to that dismal list the endeavors of the lead opinion. This is a most unfortunate and denigrating predicament for citizens who for more than one hundred years have been branded with a stigma of inferiority, and all that follows therefrom.
At the root of this problem is the unacceptable role of the courts. Their complicity in the perpetuation of this outcome is unconscionable. As in the case of racial segregation, see Plessy v. Ferguson, 163 U.S. 557 (1896) (overruled by Brown v. Bd. of Educ., 347 U.S. 482 (1954)), it is the courts that are responsible for the creation of this inequality.22 Furthermore, it is the courts that have clothed this noxious condition in a mantle of legal respectability.
But perhaps even more egregious is the fact that it is this judiciary that has mechanically parroted the outdated and retrograde underpinnings on which this invented inferiority is perpetuated. This result is now reached without so much as a minimum of analysis or consideration for the passage of time and the changed conditions, both legal and societal.23 These changed conditions have long undermined the foundations of these judge-made rules, which were established in a by-gone era in consonance with the distorted views of that epoch.24 Although the unequal treatment of persons because of the color of their skin or other irrelevant reasons, was then the modus operandi of governments, and an accepted practice of societies in general, the continued enforcement of these rules by the courts is today an outdated anachronism, to say the least. Such actions, particularly by courts of the United States, only serve to tarnish our judicial system as the standard-bearer of the best values to which our Nation aspires. Allowing these antiquated rules to remain in place, long after the unequal treatment of American citizens has become constitutionally, morally and culturally unacceptable in the rest of our Nation, see Brown v. Bd. of Educ., 347 U.S. 483, is an intolerable state of affairs which cannot be excused by hiding behind any theory of law.
The conclusions of the lead opinion in refusing to consider the merit of Appellants' claims is particularly inexcusable because, as will be further elaborated, the present decision cannot be legitimately grounded on the Supreme Law of the Land, which requires that Appellants be provided an effective judicial remedy for the correction of the wrongs they allege. See International Covenant on Civil and Political Rights, art. 2, § 3, Dec. 19, 1966, 999 U.N.T.S. 171 (hereinafter ICCPR) ("Each State Party [including the United States] ․ undertakes [t]o ensure that any person whose [ICCPR] rights are violated shall have an effective remedy," and to ensure that these rights are "determined by competent judicial, administrative, or legislative authorities․"). The suggestion that Appellants seek a political rather than a judicial remedy to correct the grievous violation of their rights claimed in this action, is, at a minimum, ironic given that it is precisely the lack of political representation that is the central issue in this case. It is this lack of any political power by these disenfranchised U.S. citizens, and the cat and mouse games that have been played with them by the United States government, including its courts, that have resulted in their interminable unequal condition.
When this status of second-class citizenship is added to the also judicially established rule that grants Congress plenary powers over the territories and their inhabitants, i.e., that recognizes in Congress practically unfettered authority over the territories and their inhabitants,26 one has to ask what effective political process is the lead opinion suggesting be turned to by Appellants to resolve the constitutional issues raised by this case? In fact, the referral by the lead opinion to the exercise of political power by these disenfranchised citizens, as the solution to their political inequality is nothing more than the promotion of the continued colonial status that has existed since Puerto Rico was acquired by the United States as booty after the Spanish–American War of 1898.27 As such, this suggestion is totally lacking in consequence or substance, and undeserving of a serious response.
With the primary vehicle for exerting effective political pressure being barred by the lack of elected voting representatives in Congress, it is a travesty to tout the political process as a means of vindicating the fundamental inequality of the United States citizens who reside in Puerto Rico. The lead opinion's ruling is the equivalent of having decided, before Brown v. Board of Education, that African-Americans should forgo their right to judicial action under the Constitution as the road map to overruling the inequality promoted by Plessy.
In 1961, just a few years after the United Nations first ratified the ICCPR, the Twenty-third Amendment to the United States Constitution was passed, allowing United States citizens residing in the District of Columbia to vote for the executive offices. As of 2009[update] a bill was pending in Congress that would treat the District of Columbia as "a congressional district for purposes of representation in the House of Representatives", and permit United States citizens residing in the capitol to vote for members of the House of Representatives.[12] However, the United States has not taken similar steps with regard to the five million United States citizens who reside in the U.S. territories, of which close to four million are residents of Puerto Rico. In an opinion concurring in part and dissenting in part in a judicial decision, Puerto Rican jurist Juan R. Torruella wrote that this inaction is in clear violation of the United States' obligations under the ICCPR.[13]
See also[edit]
Puerto Rico portal
Politics portal
Elections in Puerto Rico
Voting rights in the United States
Uniformed and Overseas Citizens Absentee Voting Act
District of Columbia voting rights
Twenty-third Amendment to the United States Constitution
Notes[edit]
Jump up ^ The Constitution originally mandated election by popular vote only for the House of Representatives, with Senators being chosen by State legislatures. The 17th amendment specified direct popular election for Senators.
References[edit]
Jump up ^ U.S. Const. art. IV, § 3, cl. 2 ("The Congress shall have Power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States...").
Jump up ^ Inter-American Commission on Human Rights (Organization of American States) REPORT Nº 98/03* Archived 2011-10-01 at the Wayback Machine.
Jump up ^ Petition to the Organization of American States Inter-American Commission of Human Rights.
Jump up ^ Igartúa–de la Rosa v. United States (Igartúa III) Archived 2012-03-16 at the Wayback Machine., 417 F.3d 145 (1st Cir. 2005) (en banc), GREGORIO IGARTÚA, ET AL., Plaintiffs, Appellants, v. UNITED STATES OF AMERICA, ET AL., Defendants, Appellees. No. 09-2186 (November 24, 2010)
Jump up ^ "Voting Residency Guidelines", Federal Voting Assistance Program
Jump up ^ Report By the President's Task Force On Puerto Rico's Status (December 2005)
Jump up ^ Report By the President's Task Force On Puerto Rico's Status (December 2007)
Jump up ^ Torruella, Juan R. (1985). Torruella, Juan R. (1985). The Supreme Court and Puerto Rico: The Doctrine of Separate and Unequal. University of Puerto Rico Press. ISBN 0-8477-3031-X.
Jump up ^ José D. Román. "Puerto Rico and a Constitutional Right to vote". University of Dayton. Retrieved 2007-10-02. (excerpted from: José D. Román, Trying to Fit an Oval Shaped Island into a Square Constitution: Arguments for Puerto Rican Statehood, 29 Fordham Urban Law Journal 1681–1713, 1697–1713 (April, 2002) (316 Footnotes Omitted))
^ Jump up to: a b Boudin, Chief Judge. "De La Rosa et al. vs. United States". Findlaw, quoting the decision by the Appeals Court of the First Circuit. Retrieved 2007-10-02.
^ Jump up to: a b c Lynch, Chief Judge. "GREGORIO IGARTÚA ET AL v. UNITED STATES OF AMERICA ET AL". Findlaw. Retrieved 2011-10-21.
Jump up ^ District of Columbia House Voting Rights Act, S. 160, 111th Cong. (passed by Senate, February 26, 2009)
Jump up ^ GREGORIO IGARTÚA ET AL v. UNITED STATES OF AMERICA ET AL (IGARTUA IV)
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James Chadwick at the 1933 Solvay Conference. Chadwick had discovered the neutron the year before while working at Cavendish Laboratory.
The discovery of the neutron and its properties was central to the extraordinary developments in atomic physics that occurred in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude model for the atom,[1]:188 [2] based on the gold foil experiment of Hans Geiger and Ernest Marsden. In this model, atoms had their mass and positive electric charge concentrated in a very small nucleus.[3] By 1920 chemical isotopes had been discovered, the atomic masses had been determined to be integer multiples of the mass of the hydrogen atom,[4] and the atomic number had been identified as the charge on the nucleus.[5]:§1.1.2 Throughout the 1920s, the nucleus was viewed as composed of combinations of protons and electrons, the two elementary particles known at the time, but that model presented several experimental and theoretical contradictions.[1]:298
The essential nature of the atomic nucleus was established with the discovery of the neutron by James Chadwick in 1932[6] and the determination that it was a new elementary particle, distinct from the proton.[7][8]:55
The uncharged neutron was immediately exploited as a new means to probe nuclear structure, leading to such discoveries as the creation of new radioactive elements by neutron irradiation (1934) and the fission of uranium atoms by neutrons (1938).[9] The discovery of fission led to the creation of both nuclear power and weapons by the end of World War II. Both the proton and neutron were presumed to be elementary particles until the 1960s when they were determined to be composite particles built from quarks.[10]
Contents
[hide]
1 Gold foil experiment
2 Discovery of isotopes
3 Atomic number and Moseley's law
4 Rutherford atom
5 Problems of the nuclear electrons hypothesis
6 Discovery of the neutron
7 Proton–neutron model of the nucleus
8 The nature of the neutron
9 Neutron physics in the 1930s
10 After 1939
11 Videos
12 References
13 Further reading
Gold foil experiment[edit]
See also: Atomic theory and Plum pudding model
A schematic of the nucleus of an atom indicating
β−
radiation, the emission of a fast electron from the nucleus (the accompanying antineutrino is omitted). In the Rutherford model for the nucleus, red spheres were protons with positive charge and blue spheres were protons tightly bound to an electron with no net charge.
The inset shows beta decay of a free neutron as it is understood today; an electron and antineutrino are created in this process.
At the start of the 20th century, the vigorous debate as to the existence of atoms had not yet been resolved. Philosophers such as Ernst Mach and Wilhelm Ostwald denied that atoms were real, viewing them as a convenient mathematical construct, while scientists such as Arnold Sommerfeld and Ludwig Boltzmann saw that physical theories required the existence of atoms.[9]:§1 Radioactivity had been recently discovered in uranium and thorium. Ernest Rutherford had separated radioactivity into three types: alpha, beta, and gamma rays, depending on their ability to penetrate, or travel into, ordinary objects or gases.[11] These radiations were soon identified with known particles: alpha rays were shown to be helium ions by Rutherford and Thomas Royds in 1907;[12] beta rays were shown to be electrons by Henri Becquerel in 1900; and gamma rays were shown to be electromagnetic radiation, that is, a form of light, in 1914.[1]:62 These radiations had also been identified as emanating from atoms, hence they provided clues as to processes occurring within atoms. Conversely, the radiations were also recognized as tools that could be exploited in scattering experiments to probe the interior of atoms.
At the University of Manchester between 1908 and 1913, Rutherford directed Hans Geiger and Ernest Marsden in a series of experiments to determine what happens when alpha particles scatter from metal foil. Now called the Rutherford gold foil experiment, or the Geiger–Marsden experiment, these measurements made the extraordinary discovery that alpha particles would occasionally scatter to high angle when passing through a thin gold foil. The scattering indicated that the alpha particles were reflecting from a small, but dense, component of atoms. Based on these measurements, by 1911 it was apparent to Rutherford that the atom consisted of a small massive nucleus with positive charge surrounded by a much larger cloud of negatively charged electrons.[2] The concentrated atomic mass was required to provide the observed reflection of the alpha particles, and Rutherford developed a mathematical model that accounted for the scattering.[2]
The Rutherford model was very influential, motivating the Bohr model for electrons orbiting the nucleus in 1913[13] and eventually leading to quantum mechanics by the mid-1920s.
Discovery of isotopes[edit]
Concurrent with the work of Rutherford, Geiger, and Marsden, the radiochemist Frederick Soddy at the University of Glasgow was studying radioactive decay chains of uranium. Soddy had been a student of Rutherford. Soddy's study indicated about 40 different radioactive elements, referred to as radioelements, between uranium and lead, although the periodic table only allowed for 11 elements.[14] By 1913 Soddy had determined that several of these elements had identical chemical properties but different atomic weights. He called these chemically similar elements isotopes.[15][16] For his study of radioactivity and the discovery of isotopes, Soddy was awarded the 1921 Nobel Prize in Chemistry.[17]
Replica of Aston's third mass spectrometer
Building from work by J. J. Thomson on the deflection of positively charged atoms by electric and magnetic fields, Francis Aston built the first mass spectrograph at the Cavendish Laboratory in 1919.[4] His aim was to try to separate the two isotopes of neon, which he was able to easily do. Aston discovered that the masses of all the particles are whole numbers, called the whole number rule, that is, the masses of all the isotopes are whole number multiples of the mass of the hydrogen atom.[18] Aston arbitrarily computed his masses relative to oxygen-16, which he took to have a mass of exactly 16. (Today the atomic mass unit (amu) is relative to carbon-12.[19]) Ironically, the one exception to this rule was hydrogen itself, which had a mass value of 1.008. The excess mass was small, but well outside experimental uncertainty. Aston and others quickly realized that the discrepancy is due to the binding energy of atoms, that is, the mass of a number of hydrogen atoms bound into a single atom must be less than the sum of the masses of the separate hydrogen atoms. Additional work determined the nuclide binding energies. Aston's work on isotopes garnered him the 1922 Nobel Prize in Chemistry for the discovery of isotopes in a large number of non-radioactive elements, and for his enunciation of the whole-number rule. [20] Noting Aston's recent discovery of nuclear binding energy, in 1920 Arthur Eddington suggested that stars may obtain their energy by fusing hydrogen (protons) into helium and that the heavier elements may form in stars.[21][22]
Atomic number and Moseley's law[edit]
Main article: Moseley's law
Rutherford and others had noted the disparity between the mass of an atom, computed in atomic mass units, and the approximate charge required on the nucleus for the Rutherford model to work. The required charge of the atomic nucleus was usually about half its atomic mass. In 1911 Antonius van den Broek made the then bold suggestion that the required charge, denoted Z, was not half of the atomic weight for elements, but instead was exactly equal to the element's atomic number, or place in the periodic table.[1]:5 At that time the positions of the elements in the table were not known to have any physical significance, except as a way to order the elements in particular sequences with similar chemical properties.
At the University of Manchester in 1913 Henry Moseley discussed the new Bohr model of the atom with the visiting Bohr.[23] The model accounted for the electromagnetic emission spectrum from the hydrogen atom, and Moseley wondered if the electromagnetic emission spectra of heavier elements such as cobalt and nickel would follow their ordering by weight, or by their position in the periodic table. In 1913-1914 Moseley tested the question experimentally by using x-ray diffraction techniques. He found that the most intense short-wavelength line in the x-ray spectrum of a particular element, known as the K-alpha line, was related to the element's position in the periodic table, that is, its atomic number, Z. Indeed, Moseley introduced this nomenclature.[5]:§1.1.2 Moseley found that the frequencies of the radiation were related in a simple way to the atomic number of the elements for a large number of elements.[24]
Within a year it was noted that the equation for the relation, now called Moseley's law, could be explained in terms of the 1913 Bohr model, with reasonable extra assumptions about atomic structure in other elements. Moseley's result, by Bohr's later account, not only established atomic number as a measurable experimental quantity, but gave it a physical meaning as the positive charge on the atomic nucleus. The elements could be ordered in the periodic system in order of atomic number, rather than atomic weight. The result tied together the organization of the periodic table, the Bohr model for the atom, and Rutherford's model for alpha scattering from nuclei. It was cited by Rutherford, Bohr, and others as a critical advance in understanding the nature of the atomic nucleus.[25]
Further research in atomic physics was interrupted by the outbreak of World War I. Moseley was killed in 1915 at the Battle of Gallipoli,[26] while Rutherford's student James Chadwick was interned in Germany for the duration of the war, 1914-1918.[27] In Berlin, Lise Meitner and Otto Hahn's work on determining the radioactive decay chains of radium and uranium by precise chemical separation was interrupted.[9]:§4 Meitner spent much of the war working as a radiologist and medical X-ray technician near the Austrian front, while Hahn, a chemist, worked on research in poison gas warfare.
Rutherford atom[edit]
Ernest Rutherford
See also: Discovery of the proton
In 1920 Rutherford gave a Bakerian lecture at the Royal Society entitled the "Nuclear Constitution of Atoms", a summary of what was then known about the nucleus of the atom.[28][8]:23 By 1920, the existence of electrons within the atomic nucleus was widely assumed. It was assumed the nucleus consisted of hydrogen nuclei in number equal to the atomic mass. But since each hydrogen had charge +1, the nucleus required a smaller number of "internal electrons" each of charge -1 to give the nucleus its correct total charge. The mass of protons is about 1800 times greater than that of electrons, so the mass of the electrons is incidental in this computation. Such a model was consistent with the scattering of alpha particles from heavy nuclei, as well as the charge and mass of the many isotopes that had been identified. There were other motivations for the proton–electron model. As noted by Rutherford at the time, "We have strong reason for believing that the nuclei of atoms contain electrons as well as positively charged bodies...",[28] namely, it was known that beta radiation was electrons emitted from the nucleus.[8]:21
In that lecture, Rutherford conjectured the existence of new particles. The alpha particle was known to be very stable, and it was assumed to retain its identity within the nucleus. The alpha particle was presumed to consist of four protons and two closely bound electrons to give it +2 charge and mass 4. In a 1919 paper,[29] Rutherford had reported the apparent discovery of a new doubly charged particle of mass 3, denoted the X++, interpreted to consist of three protons and a closely bound electron. This result suggested to Rutherford the likely existence of two new particles, one of two protons with a closely bound electron, and another of one proton and a closely bound electron. The X++ particle was later determined to have mass 4 and to be just a low-energy alpha particle.[8]:25 Nevertheless, Rutherford had conjectured[28] the existence of the neutron, a neutral particle of mass 1, and the deuteron, a +1 charge particle of mass 2. The latter is the nucleus of deuterium, discovered in 1931 by Harold Urey.[30] The mass of the hypothetical neutral particle would be little different from that of the proton. Rutherford determined that such a zero-charge particle would be difficult to detect by available techniques.
By 1921 Rutherford had named the uncharged particle the neutron,[31] while about that same time the word proton was adopted for the hydrogen nucleus.[32] Neutron was apparently constructed from the Latin root for neutral and the Greek ending -on (by imitation of electron and proton).[33][34] References to the word neutron in connection with the atom can be found in the literature as early as 1899, however.[35]
Rutherford and Chadwick immediately began an experimental program to search for the neutron at the Cavendish Laboratory in Cambridge.[31][8]:27 The experiments continued throughout the 1920s without success.[6]
Rutherford's conjecture was not widely accepted. In his 1931 textbook on the Constitution of Atomic Nuclei and Radioactivity, George Gamow, then at the Institute for Theoretical Physics in Copenhagen, did not mention the neutron.[36] At the time of their 1932 measurements in Paris that would lead to the discovery of the neutron, Irène Joliot-Curie and Frédéric Joliot were unaware of the conjecture.[37]
Problems of the nuclear electrons hypothesis[edit]
Throughout the 1920s, physicists assumed that the atomic nucleus was composed of protons and "nuclear electrons".[8]:29–32[38][39] Under this hypothesis, the nitrogen-14 (14N) nucleus would be composed of 14 protons and 7 electrons, so that it would have a net charge of +7 elementary charge units and a mass of 14 atomic mass units. The nucleus was also orbited by another 7 electrons, termed "external electrons" by Rutherford,[28] to complete the 14N atom. Obvious problems with the hypothesis became apparent, however.
Ralph Kronig pointed out in 1926 that the observed hyperfine structure of atomic spectra was inconsistent with the proton–electron hypothesis. This structure is caused by the influence of the nucleus on the dynamics of orbiting electrons. The magnetic moments of supposed "nuclear electrons" should produce hyperfine spectral line splittings similar to the Zeeman effect, but no such effects were observed.[40][8]:34 It appeared as if the magnetic moment of the electron disappeared when it was within the nucleus.
Observations of the energy levels of molecules by Franco Rasetti in 1929 were inconsistent with the nuclear spin expected from proton–electron hypothesis.[8]:35[41] Molecular Raman spectroscopy of dinitrogen (14N2) showed that transitions originating from even-numbered rotational levels are more intense than those from odd levels, hence the even levels are more populated.[1] According to quantum mechanics and the Pauli exclusion principle, the spin of the 14N nucleus is therefore an integer multiple of ħ (the reduced Planck constant).[42][43] Yet both protons and electrons carry an intrinsic spin of ½ ħ, and there is no way to arrange an odd number (14 protons + 7 electrons = 21) of spins ±½ ħ to give a spin that is an integer multiple of ħ.
The Klein paradox,[44] discovered by Oskar Klein in 1928, presented further quantum mechanical objections to the notion of an electron confined within a nucleus.[40] Derived from the Dirac equation, this clear and precise paradox showed that a high-energy electron approaching a potential barrier has a high probability of passing through the barrier, or escaping, by transforming to a particle of negative mass. Apparently, an electron could not be confined within a nucleus by any potential well. The meaning of this paradox was intensely debated at the time.[40]
By about 1930 it was generally recognized that it was difficult to reconcile the proton–electron model for nuclei with the Heisenberg uncertainty relation of quantum mechanics.[40][1]:299 This relation, Δx⋅Δp ≥ ½ħ, implies that an electron confined to a region the size of an atomic nucleus has an expected kinetic energy of 10–100 MeV.[1][45][46] This energy is larger than the observed energy of beta particles emitted from the nucleus.[1] The expected electron energy is also larger than the binding energy of nucleons, which Aston and others had shown to be less than 9 MeV per nucleon.[47]
While all these considerations did not "prove" an electron could not exist in the nucleus, they were challenging for physicists to interpret. In his 1931 textbook, Gamow summarized all these contradictions. Adding to the confusion in interpretation, the continuous energy distribution of beta decay electrons seemed to indicate that energy was not conserved by this "nuclear electrons" process. Indeed, Bohr, Gamow, Heisenberg and others considered the possibility that the laws of quantum mechanics were not applicable inside the nucleus.[8]:40[36] Such considerations were apparently reasonable, inasmuch as the laws of quantum mechanics had so recently overturned the laws of classical mechanics. The contradictions were mysterious and troublesome,[38] until it was realized that there are no electrons in the nucleus.
Discovery of the neutron[edit]
In 1930, Walther Bothe and Herbert Becker in Giessen, Germany found that if the energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium (9
4Be
), boron (11
5B
), or lithium (7
3Li
), an unusually penetrating radiation was produced. Beryllium produced the most intense such radiation. Polonium is highly radioactive, hence it is a good source of energetic alpha radiation. Polonium was commonly used for such scattering experiments at the time.[36]:99–110 Since the observed radiation was not influenced by an electric field (neutrons have no charge), it was thought to be gamma radiation. The radiation was more penetrating than any gamma rays known, and the details of experimental results were difficult to interpret.[48][49][36]
A schematic diagram of the experiment used to discover the neutron in 1932. At left, a polonium source was used to irradiate beryllium with alpha particles, which induced an uncharged radiation. When this radiation struck paraffin wax, protons were ejected. The protons were observed using a small ionization chamber. Adapted from Chadwick (1932).[6]
Two years later Irène Joliot-Curie and Frédéric Joliot in Paris showed that if this unknown radiation fell on paraffin wax, or any other hydrogen-containing compound, it ejected protons of very high energy (5 MeV).[50] This observation was not in itself inconsistent with the assumed gamma ray nature of the new radiation, but that interpretation (Compton scattering) had a logical problem. From energy and momentum considerations, a gamma ray would have to have impossibly high energy (50 MeV) to scatter a massive proton.[5]:§1.3.1 In Rome, the young physicist Ettore Majorana declared that the manner in which the new radiation interacted with protons required a new neutral particle.[51]
On hearing of the Paris results, neither Rutherford nor James Chadwick at the Cavendish Laboratory believed the gamma ray hypothesis.[52] Assisted by Norman Feather,[53] Chadwick quickly performed a series of experiments showing that the gamma ray hypothesis was untenable. The previous year, Chadwick, J.E.R. Constable, and E.C. Pollard had already conducted experiments on disintegrating light elements using alpha radiation from polonium.[54] They had also developed more accurate and efficient methods for detecting, counting, and recording the ejected protons. Chadwick repeated the creation of the radiation using beryllium and aimed the radiation at paraffin following the Paris experiment. Paraffin wax is a hydrocarbon high in hydrogen content, hence offers a target dense with protons; since neutrons and protons have almost equal mass, protons scatter energetically from neutrons. Chadwick measured the range of these protons, and also measured how the new radiation impacted the atoms of various gases.[55] He found that the new radiation consisted of not gamma rays, but uncharged particles with about the same mass as the proton. These particles were neutrons.[56][6][57][15] Chadwick won the Nobel Prize in Physics for this discovery in 1935.[58]
The year 1932 was later referred to as the "annus mirabilis" for nuclear physics in the Cavendish Laboratory,[55] with discoveries of the neutron, artificial nuclear disintegration by the Cockcroft–Walton particle accelerator, and the positron.
Proton–neutron model of the nucleus[edit]
Models depicting the nucleus and electron energy levels in hydrogen, helium, lithium, and neon atoms. In reality, the diameter of the nucleus is about 100,000 times smaller than the diameter of the atom.
Given the problems of the proton–electron model,[38][39] it was quickly accepted that the atomic nucleus is composed of protons and neutrons, although the precise nature of the neutron was initially unclear. Within months after the discovery of the neutron, Werner Heisenberg[59][60][61][15] and Dmitri Ivanenko[62] had proposed proton–neutron models for the nucleus.[63] Heisenberg's landmark papers approached the description of protons and neutrons in the nucleus through quantum mechanics. While Heisenberg's theory for protons and neutrons in the nucleus was a "major step toward understanding the nucleus as a quantum mechanical system,"[64] he still assumed the presence of nuclear electrons. In particular, Heisenberg assumed the neutron was a proton–electron composite, for which there is no quantum mechanical explanation. Heisenberg had no explanation for how lightweight electrons could be bound within the nucleus. Heisenberg introduced the first theory of nuclear exchange forces that bind the nucleons. He considered protons and neutrons to be different quantum states of the same particle, i.e., nucleons distinguished by the value of their nuclear isospin quantum numbers.
The proton–neutron model explained the puzzle of dinitrogen. When 14N was proposed to consist of 3 pairs each of protons and neutrons, with an additional unpaired neutron and proton each contributing a spin of 1⁄2 ħ in the same direction for a total spin of 1 ħ, the model became viable.[65][66][67] Soon, neutrons were used to naturally explain spin differences in many different nuclides in the same way.
If the proton–neutron model for the nucleus resolved many issues, it highlighted the problem of explaining the origins of beta radiation. No existing theory could account for how electrons could emanate from the nucleus. In 1934, Enrico Fermi published his classic paper describing the process of beta decay, in which the neutron decays to a proton by creating an electron and a (as yet undiscovered) neutrino.[68] The paper employed the analogy that photons, or electromagnetic radiation, were similarly created and destroyed in atomic processes. Ivanenko had suggested a similar analogy in 1932.[65][69] Fermi's theory requires the neutron to be a spin-½ particle. The theory preserved the principle of conservation of energy, which had been thrown into question by the continuous energy distribution of beta particles. The basic theory for beta decay proposed by Fermi was the first to show how particles could be created and destroyed. It established a general, basic theory for the interaction of particles by weak or strong forces.[68] While this influential paper has stood the test of time, the ideas within it were so new that when it was first submitted to the journal Nature in 1933 it was rejected as being too speculative.[64]
The nature of the neutron[edit]
Seventh Solvay Conference, 1933.
The question of whether the neutron was a composite particle of a proton and an electron persisted for a few years after its discovery.[70][71] In 1932 Harrie Massey explored a model for a composite neutron to account for its great penetrating power through matter and its electrical neutrality,[72] for example. The issue was a legacy of the prevailing view from the 1920s that the only elementary particles were the proton and electron. The nature of the neutron was a primary topic of discussion at the 7th Solvay Conference held in October 1933, attended by Heisenberg, Niels Bohr, Lise Meitner, Ernest Lawrence, Fermi, Chadwick, and others.[64][73] As posed by Chadwick in his Bakerian Lecture in 1933, the primary question was the mass of the neutron relative to the proton. If the neutron's mass was less than the combined masses of a proton and an electron (7000100780000000000♠1.0078 u), then the neutron could be a proton-electron composite because of the mass defect from the binding energy. If greater than the combined masses, then the neutron was elementary like the proton.[57] The question was challenging to answer because the electron's mass is only 0.05% of the proton's, hence exceptionally precise measurements were required.
The difficulty of making the measurement is illustrated by the wide-ranging values for the mass of the neutron obtained from 1932-1934. The accepted value today is 7000100865999999999♠1.00866 u. In Chadwick's 1932 paper reporting on the discovery, he estimated the mass of the neutron to be between 7000100499999999999♠1.005 u and 7000100800000000000♠1.008 u.[52] By bombarding boron with alpha particles, Frédéric and Irène Joliot-Curie obtained a high value of 7000101200000000000♠1.012 u, while Ernest Lawrence's team at the University of California measured the small value 7000100060000000000♠1.0006 u using their new cyclotron.[74]
In 1935 Chadwick and his doctoral student Maurice Goldhaber resolved the issue by reporting the first accurate measurement of the mass of the neutron. They used the 2.6 MeV gamma rays of Thallium-208 (208Tl) (then known as thorium C") to photodisintegrate the deuteron[75]
2
1D
+
γ
→ 1
1H
+
n
In this reaction, the resulting proton and neutron have about equal kinetic energy, since their masses are about equal. The kinetic energy of the resulting proton could be measured (0.24 MeV), and therefore the deuteron's binding energy could be determined (2.6 MeV - 2(0.24 MeV) = 2.1 MeV, or 6997230000000000000♠0.0023 u). The neutron's mass could then be determined by the simple mass balance
md + b.e. = mp + mn
where md,p,n refer to the deuteron, proton, or neutron mass, and "b.e." is the binding energy. The masses of the deuteron and proton were known; Chadwick and Goldhaber used values 2.0142 u and 1.0081 u, respectively. They found that the neutron's mass was slightly greater than the mass of the proton 7000100840000000000♠1.0084 u or 7000100899999999999♠1.0090 u, depending on the precise value used for the deuteron mass.[7] The mass of the neutron was too large to be a proton-electron composite, and the neutron was therefore identified as an elementary particle.[52] Ironically, in support of Fermi's theory, Chadwick and Goldhaber predicted that a free neutron would be able to decay into a proton, electron, and neutrino (beta decay).
Neutron physics in the 1930s[edit]
See also: Neutron magnetic moment, Enrico Fermi, Lise Meitner, and Otto Hahn
Soon after the discovery of the neutron, indirect evidence suggested the neutron had an unexpected non-zero value for its magnetic moment. Attempts to measure the neutron's magnetic moment originated with the discovery by Otto Stern in 1933 in Hamburg that the proton had an anomalously large magnetic moment.[76][77] By 1934 groups led by Stern, now in Pittsburgh, and I. I. Rabi in New York had independently deduced that the magnetic moment of the neutron was negative and unexpectedly large by measuring the magnetic moments of the proton and deuteron.[71][78][79][80][81] Values for the magnetic moment of the neutron were also determined by Robert Bacher[82] (1933) at Ann Arbor and I.Y. Tamm and S.A. Altshuler[71][83] (1934) in the Soviet Union from studies of the hyperfine structure of atomic spectra. By the late 1930s accurate values for the magnetic moment of the neutron had been deduced by the Rabi group using measurements employing newly developed nuclear magnetic resonance techniques.[81] The large value for the proton's magnetic moment and the inferred negative value for the neutron's magnetic moment were unexpected and raised many questions.[71]
Fermi and his students (the Via Panisperna boys) in the courtyard of Rome University's Physics Institute in Via Panisperna, about 1934. From Left to right: Oscar D'Agostino, Emilio Segrè, Edoardo Amaldi, Franco Rasetti and Fermi
The discovery of the neutron immediately gave scientists a new tool for probing the properties of atomic nuclei. Alpha particles had been used over the previous decades in scattering experiments, but such particles, which are helium nuclei, have +2 charge. This charge makes it difficult for alpha particles to overcome the Coulomb repulsive force and interact directly with the nuclei of atoms. Since neutrons have no electric charge, they do not have to overcome this force to interact with nuclei. Almost coincident with its discovery, neutrons were used by Norman Feather, Chadwick's colleague and protege, in scattering experiments with nitrogen.[84] Feather was able to show that neutrons interacting with nitrogen nuclei scattered to protons or induced nitrogen to disintegrate to form boron with the emission of an alpha particle. Feather was therefore the first to show that neutrons produce nuclear disintegrations.
In Rome, Enrico Fermi bombarded heavier elements with neutrons and found the products to be radioactive. By 1934 Fermi had used neutrons to induce radioactivity in 22 different elements, many of these elements of high atomic number. Noticing that other experiments with neutrons at his laboratory seemed to work better on a wooden table than a marble table, Fermi suspected that the protons of the wood were slowing the neutrons and so increasing the chance for the neutron to interact with nuclei. Fermi therefore passed neutrons through paraffin wax to slow them and found that the radioactivity of bombarded elements increased by a hundredfold. The cross section for interaction with nuclei is much larger for slow neutrons than for fast neutrons. In 1938 Fermi received the Nobel Prize in Physics "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons".[85][86]
Lise Meitner and Otto Hahn in their laboratory in 1913.[9]
Nuclear fission caused by absorption of a neutron by uranium-235. The heavy nuclide fragments into lighter components and additional neutrons.
In Berlin, the collaboration of Lise Meitner and Otto Hahn, together with their assistant Fritz Strassmann, furthered the research begun by Fermi and his team when they bombarded uranium with neutrons. Between 1934 and 1938, Hahn, Meitner, and Strassmann found a great number of radioactive transmutation products from these experiments, all of which they regarded as transuranic.[87] Transuranic nuclides are those that have an atomic number greater than uranium (92), formed by neutron absorption; such nuclides are not naturally occurring. In July 1938, Meitner was forced to escape antisemitic persecution in Nazi Germany after the Anschluss, and she was able to secure a new position in Sweden. The decisive experiment on 16–17 December 1938 (using a chemical process called "radium–barium–mesothorium fractionation") produced puzzling results: what they had understood to be three isotopes of radium were instead consistently behaving as barium.[9] Radium (atomic number 88) and barium (atomic number 56) are in the same chemical group. By January 1939 Hahn had concluded that he was seeing barium, lanthanum, cerium and light platinoids. Meitner and her nephew Otto Frisch immediately and correctly interpreted these observations as nuclear fission, a term coined by Frisch.[88] Hahn and his collaborators had detected the splitting of uranium nuclei, made unstable by neutron absorption, into lighter elements. Meitner and Frisch also showed that the fission of each uranium atom would release about 200 MeV of energy. The discovery of fission electrified the global community of atomic physicists and the public.[9] In their second publication on nuclear fission, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process.[89] Frédéric Joliot and his team proved this phenomenon to be a chain reaction in March 1939. In 1945 Hahn received the 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei."[90][91]
After 1939[edit]
The Trinity test of the Manhattan Project in 1945 was the first atomic bomb.
See also: Chicago Pile-1 and Timeline of particle discoveries
The discovery of nuclear fission at the end of 1938 marked a shift in the centers of nuclear research from Europe to the United States. Large numbers of scientists were migrating to the United States to escape the troubles and antisemitism in Europe and the looming war[92]:407–410 (See Jewish scientists and the Manhattan Project). The new centers of nuclear research were the universities in the United States, particularly Columbia University in New York and the University of Chicago where Enrico Fermi had relocated,[93][94] and a secret research facility at Los Alamos, New Mexico, established in 1942, the new home of the Manhattan project.[95] This wartime project was focussed on the construction of nuclear weapons, exploiting the enormous energy released by the fission of uranium or plutonium through neutron-based chain reactions.
The discoveries of the neutron and positron in 1932 were the start of the discoveries of many new particles. Muons were discovered in 1936. Pions and kaons were discovered in 1947, while lambda particles were discovered in 1950. Throughout the 1950s and 1960s, a large number of particles called hadrons were discovered. A classification scheme for organizing all these particles, proposed independently by Murray Gell-Mann[96] and George Zweig[97][98] in 1964, became known as the quark model. By this model, particles such as the proton and neutron were not elementary, but composed of various configurations of a small number of other truly elementary particles called partons or quarks. The quark model received experimental verification beginning in the late 1960s and finally provided an explanation for the neutron's anomalous magnetic moment.[99][10]
Videos[edit]
Ernest Rutherford summarizes the state of nuclear physics in 1935. (7 min., Nobelprize.org)
Hans Bethe discusses Chadwick and Goldhaber's work on deuteron disintegration. (2 min., Web of Stories)
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^ Jump up to: a b Perkins, Donald H. (1982), Introduction to High Energy Physics, Addison Wesley, Reading, Massachusetts, pp. 201–202, ISBN 0-201-05757-3
Jump up ^ Rutherford distinguished and named α and β rays on page 116 of: Rutherford, E. (1899) "Uranium radiation and the electrical conduction produced by it," Philosophical Magazine, Series 5, vol. 47, no. 284, 109–163. Rutherford named γ rays on page 177 of: Rutherford, E. (1903) "The magnetic and electric deviation of the easily absorbed rays from radium," Philosophical Magazine, Series 6, vol. 5, no. 26, 177–187.
Jump up ^ Rutherford, E.; Royds, T. (1908) "Spectrum of the radium emanation," Philosophical Magazine, Series 6, vol. 16, 313–317.
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^ Jump up to: a b c Ley, Willy (October 1966). "The Delayed Discovery". For Your Information. Galaxy Science Fiction. pp. 116–127.
Jump up ^ Others had also suggested the possibility of isotopes; for example:
Strömholm, D. and Svedberg, T. (1909) "Untersuchungen über die Chemie der radioactiven Grundstoffe II." (Investigations into the chemistry of the radioactive elements, part 2), Zeitschrift für anorganischen Chemie, 63: 197–206; see especially page 206.
Cameron, Alexander Thomas (1910). Radiochemistry. London, England: J. M. Dent & Sons, p. 141. (Cameron also anticipated the displacement law.)
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^ Jump up to: a b c d Rutherford, E. (1920). "Bakerian Lecture: Nuclear Constitution of Atoms". Proceedings of the Royal Society A. 97 (686): 374–400. Bibcode:1920RSPSA..97..374R. doi:10.1098/rspa.1920.0040.
Jump up ^ Rutherford, E. (1919). "Collision of α particles with light atoms". Philosophical Magazine. 37: 571.
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^ Jump up to: a b Glasson, J.L. (1921). "Attempts to detect the presence of neutrons in a discharge tube". Philosophical Magazine. 42 (250): 596. doi:10.1080/14786442108633801.
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Jump up ^ Pauli, W. (1985). "Das Jahr 1932 Die Entdeckung des Neutrons". Wolfgang Pauli Wissenschaftlicher Briefwechsel mit Bohr, Einstein, Heisenberg u.a. Sources in the History of Mathematics and Physical Sciences. 6. p. 105. doi:10.1007/978-3-540-78801-0_3. ISBN 978-3-540-13609-5.
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^ Jump up to: a b c d Gamow G. (1931) Constitution of Atomic Nuclei and Radiation, Oxford: Clarendon Press
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^ Jump up to: a b c Brown, Laurie M. (1978). "The idea of the neutrino". Physics Today. 31 (9): 23. Bibcode:1978PhT....31i..23B. doi:10.1063/1.2995181.
^ Jump up to: a b Friedlander, G.; Kennedy, J.W.; Miller, J.M. (1964) Nuclear and Radiochemistry (2nd edition), Wiley, pp. 22–23 and 38–39
^ Jump up to: a b c d Stuewer, Roger H. (1985). "Niels Bohr and Nuclear Physics". In French, A. P.; Kennedy, P. J. Niels Bohr: A Centenary Volume. Harvard University Press. pp. 197–220. ISBN 0674624165.
Jump up ^ Interview with Franco Rasetti Judith R. Goodstein, Caltech Oral History Project (1982)
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Jump up ^ Shultis, J. Kenneth; Faw, Richard E. (2007), Fundamentals of Nuclear Science and Engineering, CRC, 2nd edition, ISBN 1420051369
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^ Jump up to: a b c Brown, A. (1997). The Neutron and the Bomb: A Biography of Sir James Chadwick. Oxford University Press. ISBN 9780198539926.
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^ Jump up to: a b "Atop the Physics Wave: Rutherford Back in Cambridge, 1919–1937". Rutherford's Nuclear World. American Institute of Physics. 2011–2014. Retrieved 19 August 2014.
Jump up ^ Chadwick, James (1932). "Possible Existence of a Neutron". Nature. 129 (3252): 312. Bibcode:1932Natur.129Q.312C. doi:10.1038/129312a0.
^ Jump up to: a b Chadwick, J. (1933). "Bakerian Lecture.–The Neutron". Proceedings of the Royal Society A. 142 (846): 1–25. Bibcode:1933RSPSA.142....1C. doi:10.1098/rspa.1933.0152.
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Jump up ^ Heisenberg, W. (1932). "Über den Bau der Atomkerne. I". Zeitschrift für Physik. 77: 1–11. Bibcode:1932ZPhy...77....1H. doi:10.1007/BF01342433.
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Jump up ^ Heisenberg, W. (1933). "Über den Bau der Atomkerne. III". Zeitschrift für Physik. 80 (9–10): 587–596. Bibcode:1933ZPhy...80..587H. doi:10.1007/BF01335696.
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^ Jump up to: a b Iwanenko, D. (1932). "Sur la constitution des noyaux atomiques". Comptes Rendus de l'Académie des Sciences de Paris. 195: 439–441.
Jump up ^ Bacher, R.F.; Condon, E.U. (1932). "The Spin of the Neutron". Physical Review. 41 (5): 683–685. Bibcode:1932PhRv...41..683G. doi:10.1103/PhysRev.41.683.
Jump up ^ Whaling, W. (2009). "Robert F. Bacher 1905–2004" (PDF). Biographical Memoirs of the National Academy of Sciences. Archived (PDF) from the original on 2014-05-31.
^ Jump up to: a b Wilson, Fred L. (1968). "Fermi's Theory of Beta Decay". Am. J. Phys. 36 (12): 1150–1160. Bibcode:1968AmJPh..36.1150W. doi:10.1119/1.1974382.
Jump up ^ Iwanenko, D. (1932). "Neutronen und kernelektronen". Physikalische Zeitschrift der Sowjetunion. 1: 820–822.
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^ Jump up to: a b c d Breit, G.; Rabi, I.I. (1934). "On the interpretation of present values of nuclear moments". Physical Review. 46 (3): 230. Bibcode:1934PhRv...46..230B. doi:10.1103/PhysRev.46.230.
Jump up ^ Massey, H.S.W. (1932). "The passage of neutrons through matter". Proceedings of the Royal Society A. 138 (835): 460–469. doi:10.1098/rspa.1932.0195.
Jump up ^ Sime, R.L. (1996). Lise Meitner: A Life in Physics. University of California Press. ISBN 0520089065.
Jump up ^ Seidel, R.W. (1989). Lawrence and his Laboratory: A History of the Lawrence Berkeley Laboratory. University of California Press. ISBN 9780520064263.
Jump up ^ Chadwick, J.; Goldhaber, M. (1934). "A nuclear photo-effect: disintegration of the diplon by gamma rays". Nature. 134 (3381): 237–238. Bibcode:1934Natur.134..237C. doi:10.1038/134237a0.
Jump up ^ Frisch, R.; Stern, O. (1933). "Über die magnetische Ablenkung von Wasserstoffmolekülen und das magnetische Moment des Protons. I / Magnetic Deviation of Hydrogen Molecules and the Magnetic Moment of the Proton. I". Zeitschrift für Physik. 84: 4–16. Bibcode:1933ZPhy...85....4F. doi:10.1007/bf01330773.
Jump up ^ Esterman, I.; Stern, O. (1933). "Über die magnetische Ablenkung von Wasserstoffmolekülen und das magnetische Moment des Protons. II / Magnetic Deviation of Hydrogen Molecules and the Magnetic Moment of the Proton. I". Zeitschrift für Physik. 85: 17–24. Bibcode:1933ZPhy...85...17E. doi:10.1007/BF01330774.
Jump up ^ Esterman, I.; Stern, O. (1934). "Magnetic moment of the deuton". Physical Review. 45 (10): 761(A109). Bibcode:1934PhRv...45..739S. doi:10.1103/PhysRev.45.739.
Jump up ^ Rabi, I.I.; Kellogg, J.M.; Zacharias, J.R. (1934). "The magnetic moment of the proton". Physical Review. 46 (3): 157. Bibcode:1934PhRv...46..157R. doi:10.1103/PhysRev.46.157.
Jump up ^ Rabi, I.I.; Kellogg, J.M.; Zacharias, J.R. (1934). "The magnetic moment of the deuton". Physical Review. 46 (3): 163. Bibcode:1934PhRv...46..163R. doi:10.1103/PhysRev.46.163.
^ Jump up to: a b Rigden, John S. (2000). Rabi, Scientist and Citizen. Harvard University Press. ISBN 9780674004351.
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Jump up ^ Tamm, I.Y.; Altshuler, S.A. (1934). "Magnetic Moment of the Neutron". Doklady Akademii Nauk SSSR. 8: 455. Retrieved 30 January 2015.
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Jump up ^ "The Nobel Prize in Physics 1938: Enrico Fermi – Biographical". Nobelprize.org. Retrieved 18 November 2017.
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Jump up ^ "The Nobel Prize in Chemistry 1944: Otto Hahn – Biographical". Nobelprize.org. Retrieved 18 November 2017.
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Further reading[edit]
Annotated bibliography for neutrons from the Alsos Digital Library for Nuclear Issues
Abraham Pais, Inward Bound, Oxford: Oxford University Press, 1986. ISBN 0198519974.
Herwig Schopper, Weak interactions and nuclear beta decay, Publisher, North-Holland Pub. Co., 1966. OCLC 644015779
Ruth Lewin Sime, Lise Meitner: A Life in Physics, Berkeley, University of California Press, 1996. ISBN 0520208609.
Roger H. Stuewer, "The Nuclear Electron Hypothesis". In Otto Hahn and the Rise of Nuclear Physics, William R. Shea, ed. Dordrecht, Holland: D. Riedel Publishing Company. pp. 19–67, 1983. ISBN 90-277-1584-X.
Sin-Itiro Tomonaga, The Story of Spin, The University of Chicago Press, 1997. ISBN 9780226807942
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