Inclusive and exclusive preequilibrium spectra in a model of independently interacting excitons

Abstract

Starting from a previous ansatz of independently interacting excitons the more refined model INCLUSIVE INDEX is developed yielding inclusive preequilibrium proton and neutron spectra. It is shown that three stages are sufficient to describe single-and multinucleon emission to all orders of practical importance. By use of recurrence relations the loss of particles and energy due to emission from previous stages is fully accounted for. In order to predict the population of specific residual nuclei the precompound process is reformulated in terms of exclusive emission spectra. This intricate statistical problem is solved in the EXCLUSIVE INDEX model by algorithms representing the average probability for a specified number of particles not to be emitted but to reach the next stage of nuclear relaxation. Differential excitation probabilities can be calculated for those six nuclei which are populated by the emission of none, one, or two preequilibrium nucleons in two stages via alltogether 15 principal paths. Typical features of the INCLU-SIVE and EXCLUSIVE INDEX model are discussed. The strength of one-and twonucleon emission is compared with HYBRID model predictions. PACS:24.60J)r, 24.60.Gv

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.…”

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

“…state density at the Fermi level is related to Ev through EF = 1.5 A/g. For simplicity, we assume g~=gv=g/2 [1]. Our preferred choice is g=A/ 13.3 MeV-1 corresponding to a maximum hole depth Ev = 20 MeV.…”

“…With the indices ~ indicating protons and v neutrons we have initially p~, p~, h~ and h~ exciton particles and holes. In short notation, this set of initial exiton numbers is written no(p~, p~) with h=no-pv-p~, if we omit to specify the particular hole type as in the EXCLUSIVE INDEX model [1]. The initial exciton numbers need not to be integers so that a continuous averaging between succeeding integers is possible.…”

“…In a previous paper [1] we have introduced the IN-DEX model of precompound reactions on the basis of independently interacting excitons. It is able to predict inclusive nucleon spectra (INCLUSIVE IN-DEX model) as well as excitation functions (EXCLU-SIVE INDEX model).…”

“…A forthcoming paper [5] is subject to an exhaustive comparison of the EXCLUSIVE INDEX model with experimental excitation functions. The comparisons are carried out for reactions in which the initial excitation energy is high enough to allow for PE multi-nucleon emission.…”