Nuclear charge dispersion of light-mass fission products in the fission of 235 U and 238 U by medium-energy protons

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J.-L. GALINIER, M. DIKSIC, and L. YAFFE. Can. J. Chem. 55,3609 (1977). Cross sections for the independent formation of 76As and 78As, for the partially cumulative formation of 77As and 77Ge, and the cumulative formation of 79As, 78Ge, and 75Ge formed in the fission of 238U by protons of energies 35-85 MeV have been determined. Charge dispersion curves have been obtained. Values of (Z, -Z,) and full-widths at half-maximum of the curves show that the behaviour of these light-mass products is the same as their complementary fragment (A z 152). This is inconsistent with values found at A = 96. Chem. 55,3609 (1977). On mesure les sections efficaces pour la formation independante de 76As et 78As, la formation cumulative partielle de 77As, 77Ge, ainsi que pour la formation cumulative de 79As, 78Ge et 75Ge issus de la fission de Z38U par des protons ayant des energies comprises entre 35 et 85 MeV. Des courbes de distribution de charge sont ainsi obtenues. Les valeurs de ( Z , -Z,) et les largeurs a mi-hauteur de ces courbes indiquent que les produits ayant des masses legeres se comportent de la meme maniere que leurs complements lourds ( A z 152). Ceci est en desaccord avec les valeurs trouvtes a A = 96. [Traduit par le journal] IntroductionCharge distribution in the fission of heavy nuclei has been the object of numerous studies. In the 20-85 MeV range, the McGill group has produced a substantial body of experimental data, particularly for the proton fission of 238U (1-7). Charge dispersion curves have been found to be adequately represented by a Gaussian distribution. The study of the dependence of charge distribution parameters on the excitation energy imparted to the target nucleus shows that, for a given mass chain, Z,, the most probable charge, moves towards stability with increasing incident energy, whereas the width of the distributions increases correlatively. Both effects are found to be more pronounced in the heavy partner (1, 4) than in the light one (3) when one considers the type of asymmetric mass split which is most probable ( Z = 55 and Z = 38 regions respectively). Symmetric mass divisions yield intermediate results so far as the rate of displacement of Z, is concerned (6). Recent results obtained show that in the case of very asymmetric fission, changes in Z,, are less sensitive to increases in incident energy and that only narrow charge distribution curves are compatible with the

Section: (C) Activity Measurements and Treatment Of Datamentioning

confidence: 67%

“…In the 20-85 MeV range, the McGill group has produced a substantial body of experimental data, particularly for the proton fission of 238U (1)(2)(3)(4)(5)(6)(7). Charge dispersion curves have been found to be adequately represented by a Gaussian distribution.…”

Section: Introductionmentioning

confidence: 99%

Nuclear charge dispersion studies in the light-mass region formed in the fission of ²³⁸U by protons of energy 35–85 MeV

Galinier¹,

Dikšić²,

Yaffe³

1977

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“…Nevertheless, a variety of fissile systems (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) has been studied at medium energies.…”

Section: Introductionmentioning

confidence: 99%

Nuclear charge distribution in the region of symmetric fission of ²³⁸U by protons of energy 20–85 MeV

Sarkar¹,

Yaffe²

1976

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Independent formation cross sections in the fission of 238U by protons of energy 20-85 MeV were obtained for the nuclides IllAg, 112Ag, "7In, 115111, IllPd, and "5Cd. The last three mentioned were estimated on the basis of measurements and isomeric yield data. Charge dispersion curves were constructed and Z,, the most probable charge, determined. The values for (ZA -Z,) lie intermediate between those measured for fission products of higher and lower mass. The number of neutrons emitted was estimated and found to be higher than in asymmetric fission, leading to the conclusion that the former are events arising from higher deposition energies.

“…A number of studies on nuclear charge dispersion in the fission of heavy-mass targets by protons of energies 20-85 MeV have been reported (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). In all these studies the displacement of the most probable charge, Z,, from the charge, Z,, corresponding to stability for mass A has been measured.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Charge Dispersion in the Fission of ²³⁵U by Protons of Energy 20–85 MeV

Saha¹,

Tomita²,

Yaffe³

1971

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Independent formation cross sections of Iz9Cs, I3OCs, 13'Cs, 134C~m, 1 3 4 C~m + g , 1 3 6 C~, l3"Ce, and cumulative formation cross sections of 141Ce and 143Ce were obtained when Z35U was caused to fission with protons of energies varying between 20 and 85 MeV. The energies a t which the excitation functions reached their maxima were related to the neutron-to-proton ratio of the fission products. These were compared with other fissioning systems. Charge dispersion curves were obtained from the cross section data. The variation of ( Z , . ,-2,) with energy, both in magnitude and in trend, agrees extremely well with predictions made by Saha and Yaffe for nuclides in this mass range. Calculations for Z, show that good agreement is obtained with the unchanged charge division hypothesis. An estimate has been made of the total number of neutrons emitted in fission at these energies.