The yields of the isomers of 81Se and 83Se in the thermal neutron fission of 239Pu

Croall, I.F.; Willis, H.H.

doi:10.1016/0022-1902(63)80384-x

Cited by 20 publications

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“…Isomeric yield ratio of the high-spin to low-spin fission product isomers is related to the initial angular momentum distribution of fission fragments which emit prompt neutrons and prompt gammas to the fission product isomers. The angular momentum density distribution P(J) has been calculated by several groups [2,3,12] using statistical model:…”

Section: Discussionmentioning

confidence: 99%

Isomeric yield ratio of fission product148Pr in235U(n th,f)

1984

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The independent isomeric yield ratio of 148Pr in thermal neutron induced fission of 2asU has been determined experimentally. The fission product 14~pr isomers, extracted directly by on-line mass separation technique, have high-spin (J=4) to low-spin (J= 1) isomer ratio of 0.14 + 0.04 using growth and decay analysis. Statistical model calculation of isomeric yeild ratio using constant initial r:m.s, angular momentum J~ms can not reproduce either present results or other recent measurements of isomer ratios. The Jrms derived from isomer ratio data in all thermal fissioning systems indicate a wide spread ranging from 2h to 13h. No clear correlation between Jrm~ and isomeric spins or number of neutrons of isomers is found, thus, more model refinements and experimental works should be done in order to evaluate independent isomeric yields correctly.

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Section: Discussionmentioning

confidence: 99%

Isomeric yield ratio of fission product148Pr in235U(n th,f)

1984

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“…All nuclei which reach a low-lying state with a spin greater than the high-spin isomer are assumed to be trapped in the high-spin state, while all nuclei below this cut-off contribute to the low-spin yield. Croall and Willis (1963) have applied this technique to Se fragments in thermal neutron fission of 239Pu and derive a value for the primary fragment angular momentum J = 8. In thermal neutron fission of 235U, Sarantites et a1 (1965) similarly found J = 6 for T e fragments.…”

Section: Fission Dynamics and Angular Momentummentioning

confidence: 99%

The fission process

Grant

1976

Rep. Prog. Phys.

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As a fissioning nucleus passes from its ground state to the scission point-the point where it breaks into two fragments-the sequence of shapes it follows depends principally on the potential energy surface of the deformed nucleus. The main features of the potential energy surface are now well established. In this review the theoretical techniques used to predict the potential energy are described and the predictions are tested against theory. Other properties of nuclei on the path to scission are also discussed: the structure of individual low-lying states, level densities at high excitation, and the magnitude of inertial parameters may all be important in determining the nature of the fission process. Finally, the current state of knowledge about specifically dynamical effects in fission is summarized. This is a topic attracting a great deal of attention at present, and although relevant data are still few and the theory is rudimentary, a rough picture of fission dynamics is already building up.

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Possible exit channel effect on isomer yield ratios

Kildir

Morel

Büyükmumcu

et al. 1997

J Radioanal Nucl Chem

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Isomer yield ratio measurements in fission are important in understanding the fission process. With the development of new instrumental techniques, a large number of yield data are now available. The experimental data on isomer yield ratios in the thermal neutron induced fission of 235U are compared with those calculated from the simple statistical model by MADLAND and ENGLAND. The method of calculation has been extended to the isotopes having more than one isomeric stale. The results may be explained according to the multi-exit-channel model of fission.

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The yields of the isomers of 81Se and 83Se in the thermal neutron fission of 239Pu

Cited by 20 publications

References 10 publications

Isomeric yield ratio of fission product148Pr in235U(n th,f)

Isomeric yield ratio of fission product148Pr in235U(n th,f)

The fission process

Possible exit channel effect on isomer yield ratios

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