Isomeric cross-section ratio for the formation of73m,gSe in various nuclear processes

Abstract

The isomeric cross-section ratio 0. /(0. +erg) for the formation of" Se was determined in the ' Ge(a, n) reaction over the energy range of 13-27 MeV, in the ""Ge('He, xn) process over 13-24 MeV, in the 'As(p, 3n) reaction over 25-45 MeV, and in the ' As(d, 4n) reaction over 28-56 MeV.Measurements were done radiochemically using the "stacked-foil" technique. In (a, n) and ('He, xn) processes the ratio is relatively high at low incident particle energies but decreases with increasing energy. In (p, 3n) and (d, 4n) reactions, on the other hand, it is practically constant. Statistical model calculations taking into account precompound emission were carried out on the four processes investigated in this work as well as on the ' Se(n, 2n) reaction reported in the literature. The total cross section (o +og) is described well by the calculation. The calculated isomeric cross-section ratio depends strongly on the input level scheme of the product nucleus. In general, however, the statistical model, under a suitable set of global assumptions, can reproduce the isomeric crosssection ratio in all the five nuclear processes.

Cross sections and isomeric cross-section ratios in the interactions of fast neutrons with isotopes of mercury

“…With the increasing incident neutron energy the ratio increases, showing that at higher excitation energies the formation of the high-spin isomer is more favored. This trend is similar to that for several other neutron-and charged-particle-induced reactions near their thresholds [16,17,[39][40][41][42][43][44]. The increase seems to be more pronounced for 195 Hg m,g than for 197 Hg m,g .…”

“…Worth noting is that not only isomeric pairs with small differences in spins can be described by the model calculations (cf., for example, Refs. [17,[39][40][41][42][43][44]) but also the pairs with relatively large spin differences (as in this work), provided the input parameters are properly chosen. In this regard, two factors need special consideration: first, the input level scheme up to the continuum, and second, the spin distribution of the level density (η).…”

“…Refs. [39,41,42,44]). In the present work dealing with mercury isotopes, better results are obtained using a relatively low η value (<0.25).…”

Activation cross section and isomeric cross section ratio for the 76Ge(n,2n)75m,gGe process

“…This trend is similar to that for several other neutron-and charged-particle-induced reactions near thresholds [35][36][37][38][39][40][41][42][43][44]. In the range of 13-15 MeV, the calculated isomeric cross section ratio shows the same slightly increasing trend for the six ldmodels.…”

Formation of high-spin neodymium and mercury isomers in neutron and charged particle induced nuclear reactions

“…In the present work the emphasis was on the isomeric cross sections. Since such calculations are strongly dependent on the input level scheme of the product nucleus [6], we chose those parameters carefully. The energies, spins, parities and branching ratios of discrete levels were extracted by using the NNDC On-Line Data Service from the ENSDF database.…”