Proton Induced Reactions of Thorium—Fission Yield Curves

Tewes, H.A.; James, Ralph A.

doi:10.1103/physrev.88.860

Cited by 56 publications

(6 citation statements)

References 8 publications

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“…This value is about equal to our calculated difference. Radiochemical results by Coryell, 46 Tewes and James, 46 Schmitt and Sugarman, 47 and Steinberg and Glendenin 48 also indicate smaller neutron emission probability for symmetric fission.…”

Section: Asymmetric Fissionmentioning

confidence: 97%

Statistical Theory of Nuclear Fission: Asymmetric Fission

Fong

1956

Phys. Rev.

276

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A statistical theory is developed, according to which the relative probability of a mode of fission is determined by the total excitation energy of its two fragments calculated at the moment just before separation. In order to calculate the excitation energy, the well known semiempirical atomic mass formula is corrected for its deviations known to be attributed to the effects of nuclear shells. The nuclear level density expression is studied empirically with special attention to shell effects. These results are used for a quantitative calculation of the relative probabilities of all possible modes of fission. The mass distribution curve of fission products of U 235 induced by thermal neutrons is derived and compared with experimental results. Applications of the statistical theory to charge distribution, kinetic energy distribution, variations of mass, charge and energy distributions with respect to target nucleus and incident energy, prompt neutron distribution, spontaneous fission yields, and ternary fission will be discussed briefly.* This paper is based on a Ph.D. thesis submitted to the Department of Physics, University of Chicago, December, 1953. Preliminary results have been published in a Letter to the Editor [Peter Fong, Phys. Rev. 89, 332 (1953)]. fNow

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Section: Asymmetric Fissionmentioning

confidence: 97%

Statistical Theory of Nuclear Fission: Asymmetric Fission

Fong

1956

Phys. Rev.

276

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“…[3][4][5][6][7][8][9] With increasing mass of the fissioning nucleus, the light group distribution shifts toward higher masses, while the heavy group remains relatively constant, with perhaps a slight shift in the direction of smaller masses. 3 A tendency toward wider mass distribution with increasing mass of the fissile nucleus has also been noted.…”

Section: Introductionmentioning

confidence: 99%

Ytterbium-167

Handley

Olson

1954

Phys. Rev.

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“…The cross-section data were converted into charge distribution curves for five bombarding energies by means of the mass yield data available in the literature and the total The3? (p,f) cross-section clata of Tewes and James (33) and of Steiiler and Jungermail (32). The product of the fission yield for a given mass A and the total fission cross section gives the cumulative formation cross section for mass A.…”

Section: Resultsmentioning

confidence: 99%

“…In spontaneous fission (31) and in the fission of U233, UZ3j, and P~'~9 v i t h neutrons of thermal energy, the familiar double-peaked distribution, correspondi~lg to a preponderance of asymmetric fission modes, is observed (30). As the energy of bombarding particles is increased the mass distribution in the fission of these and other heavy nuclei becomes more and more symmetric (18,33) and a t sufficiently high energies a singly peaked distribution is observed (19).…”

Section: Introductionmentioning

confidence: 99%

DISTRIBUTION OF NUCLEAR CHARGE IN THE PROTON-INDUCED FISSION OF Th²³²

Pate¹,

Foster²,

Yaffe³

1958

Can. J. Chem.

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The cross sections for the independent formation of 1131, '~' c I~~, 11=, and 113' a~l d for the cumulative formation of T C '~~, IIJ3, and in the proton-induced fission of Th232 have been measurecl a t nine proton energies between 8 and 87 Me\-. From these data and from published total chain yield data, chargc distribution curves havc becn obtained. These are compared with published chargc distribution curves for ~~r a n i u m fission a t energies up to 480 Mev and together they show a shift of the most probable fission product charge toward stability and a widcning of the distribution with increasing bombarding energy. These phenomena are interpreted in terms of current models for nuclear reactions. INTRODUCTIONA voluminous literature exists on the distribution of nuclear mass in the fission process. In spontaneous fission (31) and in the fission of U233, UZ3j, and P~'~9 v i t h neutrons of thermal energy, the familiar double-peaked distribution, correspondi~lg to a preponderance of asymmetric fission modes, is observed (30). As the energy of bombarding particles is increased the mass distribution in the fission of these and other heavy nuclei becomes more and more symmetric (18, 33) and a t sufficiently high energies a singly peaked distribution is observed (19).About the nuclear charge distribution less is known. Data exist on the distribution from the fission of US3 with thermal neutrons (6, 7, 21) and with l4-3/Iev neutrons (34). Data also exist for the fission of uranium by 170-Mev protons ( I ) , of bismuth by 190-Mev deuterons (lo), and of uranium, thorium, and bismuth by 480-Mev protons (16), and there is fragmentary informati011 from other systems. T h e present work was undertaken to investigate the changes that occur in the charge distribution from protoninduced fission of T h T 3 h s the bombarding energy is raised from 8 to 90 hilev, the maximum proton energy of the McGill synchrocyclotron. This energy range is of interest in view of the substantial changes observed in the mass distribution (33). Also in this interval a change presumably begins in the nature of the initial step in nuclear reactions, from simple compound nucleus formation to a mechanism of direct interaction with individual nucleons (29). Thus a t the lower energies studied, excitation of the nuclei a t the end of the first step of the reaction will be essentially monochromatic whereas a t the higher end of the bombarding energy range, a broad spectrum of excitation energies will be produced, with corresponding complexity of the reaction products observed. Ideally, in the determination of a charge distribution, one would wish to measure the independent yields of each of the nuclides in one or more fission chains. This, ho~vever, is precluded by the short half-lives of most of the members of any given mass chain. One substitutes a determination of independent yields of accessible nuclides in chains of different mass number, followed by correlation of these data. Correlation is customarily attempted by means of semiempirical ...

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Proton Induced Reactions of Thorium—Fission Yield Curves

Cited by 56 publications

References 8 publications

Statistical Theory of Nuclear Fission: Asymmetric Fission

Statistical Theory of Nuclear Fission: Asymmetric Fission

Ytterbium-167

DISTRIBUTION OF NUCLEAR CHARGE IN THE PROTON-INDUCED FISSION OF Th²³²

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Proton Induced Reactions of Thorium—Fission Yield Curves

Cited by 56 publications

References 8 publications

Statistical Theory of Nuclear Fission: Asymmetric Fission

Statistical Theory of Nuclear Fission: Asymmetric Fission

Ytterbium-167

DISTRIBUTION OF NUCLEAR CHARGE IN THE PROTON-INDUCED FISSION OF Th232

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DISTRIBUTION OF NUCLEAR CHARGE IN THE PROTON-INDUCED FISSION OF Th²³²