Analysis of inclusive nucleon spectra fromp- and?-induced reactions in the frame of the INDEX model, and implications for stopped ??-induced reactions

Abstract

The previously published INDEX model is tested for nucleon spectra from p-and einduced reactions. The results of two alternative versions, the INCLUSIVE INDEX model and the EXCLUSIVE INDEX model, quite well agree with the data. It is found that in the INCLUSIVE INDEX model three preequilibrium stages are sufficient to describe single-and multi-nucleon emission. The model provides an useful first order estimate of the influence of the finite Fermi energy on particle spectra. This effect is very strong for nucleon induced reactions while for c~-induced reactions it can be neglected. The deduced mean-free-path multiplier corroborates the long stated discrepancy between models in which excitons interact independently or not. Using preequilibrium parameters similar to those found for nucleon induced reactions the important branching ratio of contributing np and pp pairs in stopped r~--absorption can be determined by INDEX model calculations. Deduced values from published n-and p-spectra agree reasonably well with those of other experimental analyses but deviate significantly from microscopic model predictions.

Activation cross sections and isomeric ratios in reactions induced by 14.5 MeV neutrons on152Sm,154Sm and178Hf

“…The computer codes used for the purpose are COMPLEX (INDEX) [25][26][27][28] and STAPRE [4]. In COMPLEX n, p, ~, d, t and 3He particles are evaporated from the formed compound nucleus (CN), according to the model of WeisskopfEwing [29] and the PE emission of n, p and e is performed in the frame of the Independent Exciton (INDEX) model.…”

Nuclear Reactions Induced by Alpha Particles on Natural Ytterbium

“…Recently a model -the Index model -was developed [11,12,13], and a code [14] capable of calculating exciation functions was built. With this code, the excitation functions for all the a induced reactions on each stable isotope of ytterbium were obtained.…”

Excitation functions and isomeric ratios in the reaction130Te (?,xpyn) for ?-particle energies between 15 and 37 MeV

“…[29,15] and IN-DEX [9][10][11]30]. Both codes are based on the same philosophy and predict the yield of residual nuclei in nuclear reactions with excitation energy up to 200 MeV taking into account two main mechanisms.…”

“…Two theoretical model codes -COMPLEX (INDEX) [9][10][11] and STAPRE [12], which describe the processes of preequilibrium and equilibrium emission in reactions with light and heavy ions, are analyzed in comparison with the measured EF and IR. In COMPLEX the mechanism of equilibrium emission is performed in the terms of the Weisskopf-Ewing model [13] and includes the evaporation of n, p, e, d, t and 3He particles, while in STAPRE n, p, e and d are evaporated and equilibrium ?,-emission is included according to the model of Hauser and Feshbach [14].…”