Mass Distribution of Fission Products from Moderately Excited ²³⁶U Compound Nucleus

Abstract

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.

Mass and charge distribution in232Th(?, f) reaction in the projectile energy range 28 to 72 MeV

“…The asymmetric mass distribution at each energy shows a peak corresponding to the symmetric region which gradually becomes more prominent at the higher excitations. Similar peaks and also similar yield-mass distribution were observed by Roginski et al [2] upto the incident beam energy of 41 MeV and by Guin et al [4] at 38.5 MeV.…”

“…The dots denotes the reflected points. The data of Guin et al [3,4] are denoted by triangles. The typical error in the experimental data are around 20%.…”

“…The error bars are not shown to avoid clumsiness 71. 4 MeV. But what is perhaps more important is that the mass distribution has changed a little over a range of excitation from about 23 to 66 MeV.…”

“…However, there are only a few such studies covering a wide range of excitation of the composite system 236U* [ 1 ]. The mass distribution in the fission of 236U was studied by various authors in the bombarding energy range 20 to 44 MeV [1][2][3][4]. However, there are practically no data at still higher excitations.…”

Mass Distribution in 12C Induced Fission of 232Th

“…Kudo et al [1] have observed the asymmetry in the mass division in the proton induced fission of 232 Th up to energies of 21 MeV and that the peak to valley ratio (P/V) decreases with increasing excitation energy. Similar observations were made in the α particle induced fission of 232 Th [2,3] at 28.5 and 38.5 MeV. On the other hand the mass distributions in the α particle induced fission of 233 U [4], 238 U, 237 Np [5] and 239 Pu [6] at excitation energies of the order of 35 MeV or more are symmetric.…”