In the present work the influence of initial excitation energy and angular momentum of the fissioning system on the angular momenta of fission fragments corresponding to ' 'Te and ' Te was studied in the Th(a3OM, v, f) system. The fragment angular momenta were estimated from the radiochemically determined independent isomeric yield ratios using a statistical model. The obtained data are discussed along with the literature data on the fragment angular momenta in the same fissioning nucleus 23 U formed in the U(n, h, f) and " Th(a, f}systems.NUCLEAR REACTIONS~~Th(a3O M v f) reaction, fragment angular momentum, independent isomeric yield ratio, initial excitation energy, angular momentum, single particle effect.

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The chain yields of 30 fission products were determined in 38 MeV a-particle induced fission of ^'^Th. The mass yield curve was found to be primarily asymmetric with a peak to Valley {pj v) ratio of 3.5. A small peak has also been observed in the Symmetrie region. The observed pjv ratio has been resolved into the pjv ratios of the individual mass distributions of the possible fissioning isotopes of uranium formed as a result of multichance fission. An attempt has been made to explain the pjv ratios thus obtained in the light of the available excitation energy in the system.

In the present work rms angular momenta have been deduced for the fission fragments corresponding to 131Tem'g and 133Tem'g in 232Th(~zr f) and 238U(e40MeV, f) systems from the radiochemically determined independent isomeric yield ratios and statistical model based analysis. For 131Te and 133Te the rms angular momenta deduced are 5.9-t-1.0 and 7.9___ 1.2 ta respectively in z3aTh(e4oMev, f) and 7.2+_0.6 and 8.0+0.8 ra respectively in z3SU(~ 4oraev,j~-c~ Comparison of the present data with the literature data for these fragments in the same compound nuclei 236U* and 24Zpu* at lower excitation energies shows increase in the fragment angular momentum with increasing excitation energy and angular momenta of the fissioning nuclei. Fragment angular momentum deduced theoretically for asymmetric and deformed fragments on the basis of thermal equilibration of the collective rotational degrees e.g., rigid rotation, wriggling, tilting, bending and twisting modes considering the effect of multichance fission, are in good agreement with the experimental observations.

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