Isomeric yield ratios of 30 fission products in 24 MeV proton-induced fission of238U were measured by the use of the ion-guide isotope separator on-line. The obtained isomeric yield ratios were converted to the angular momenta of primary fission fragments based on the statistical model. The deduced angular momenta were examined from various aspects. It is found that in general the angular momentum continuously increases with the fragment mass number including the region of symmetric mass division. However, there are some exceptions. For Sn isotopes the deduced angular momenta are quite small due to the spherical shape of the nuclear shell configuration. It is also concluded from the consideration of the charge distribution that the angular momentum of fission product scatters considerably within the narrow range of mass division. The dependence of the angular momentum on the available energy of fragments at scission point indicates that the individual fragment possesses a characteristic deformation at scission and/or the deduced angular momentum is seriously affected by the particle excitation after scission.

Isomeric yield ratios of fission products in the system of 24 MeV proton-induced fission of238U

Isomer ratios have been measured in Sb and Te isotopes prepared in the 115In( alpha ,n), 115In( alpha ,3n), 118,120,122,124Sn( alpha ,pn), and 120Sn( alpha ,3n) reactions, using a range of bombarding energies between 16.6 and 38.4 MeV. In most of the product nuclei the isomer ratios are smaller than the predictions of the sharp cut-off model, showing that the isomer is less than 100% efficient in trapping high-spin products. The variation of isomer ratio with bombarding energy is described by a simple expression for the trapping efficiency.

https://iopscience.iop.org/article/10.1088/0305-4616/5/12/013/pdf

Isomer ratios in antimony and tellurium isotopes

We report the first experimental determination of independent isomeric yield ratios using direct ion counting with a Penning trap, which offered such a high resolution in mass that isomeric states ...

/pdf/first-isomeric-yield-ratio-measurements-by-direct-ion-1lxmydc2f0.pdf

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

Angular momentum partition in heavy ion induced fission and the effects of shells on gamma-ray multiplicities

Isomeric fission yield ratios for odd-mass Cd & In isotopes using the Phase-Imaging Ion-Cyclotron-Resonance technique

/pdf/isomeric-fission-yield-ratios-for-odd-mass-cd-and-in-3xl28v42ae.pdf

Isomeric fission yield ratios for odd-mass Cd and In isotopes using the phase-imaging ion-cyclotron-resonance technique

Isomer ratios in antimony and bromine fission fragments have been measured in the (12C+209Bi), ( alpha +204Pb) and (12C+196Pt) reactions, The values of the isomer ratios and their variation with energy are in accordance with the fragment angular momenta predicted by the Fermi gas model for the fissioning nucleus.

J G Cuninghame

Papers

Isomer ratios in fission fragments at high excitation