Preequilibrium neutron emission in109Ag(3He,xn) and111Cd(p, xn) reactions

Abstract

Excitation functions of the reactions l~ xn) and mCd(p, xn) have been measured with stacked foil techniques for projectile energies E<__45 MeV and multiplicities x<__4 populating ground and spin isomeric states in 112-XIn. Preequilibrium (PE) contributions are more pronounced for the p than for the 3He entrance channel and for low multiplicities x and can be reproduced with the (geometry dependent) hybrid model. The observed isomeric cross section ratios require a reduced population for the high spin state (as compared with the expectation for equilibrated systems) whenever PE emission contributes significantly. Calculations for a full statistical model with a PE decay mode and approximate angular momentum conservation indicate PE neutron emission to be stretched in angular momentum space. For the (p, xn) reactions a more detailed coupling scheme is imperative whereas the (3He, xn) data suggest the competitive PE emission of complex particles.

Nuclear model calculation and targetry recipe for production of 110mIn

“…6. As can be seen, the model calculations are in good agreement with the experimental values (Tárkányi et al 1994;Marten et al 1985;Skakun et al 1975;Otozai et al 1966). Isomeric ratios show consistent trends in the case of 111 Cd(p,2n) 110m/g In reaction, in agreement with the theoretical calculation.…”

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

“…Similar discrepancies can be seen for (p, 3n) and (p, pn) reactions on ~9VAu in a recent study [7]. The inclusion of higher angular momentum depletion by preequilibrium emitted nucleons improved the situation for p, c~ and 3He induced reactions [5,8].…”

“…Later the normalized probabilities for populating the final nucleus B and its spin distribution were calculated in the same way as described in [8].…”

“…Following the formulation given in [8], a subroutine was added to the code STAPRE to account for the population of final states over spin after PE emission. The main assumption made, is that the angular momentum of the ejectile lb is parallel to that of the projectile Is, which implies the assumption of predominance of PE emission at the first step and forward peaked angular distribution.…”

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

“…The main assumption for such calculation was that PE emission occurs after the first interaction of the projectile in the target and that the PE particles are emitted exclusively in the forward direction [31]. Such a correction was imposed by the incapability of the code to give reasonable predictions for experimental isomeric ratios in reactions with p, 3He and c~-particles -the cross sections for populating the high spin isomeric state were overestimated without it [32,31]. The applicability of both versions of STAPRE for 14 MeV neutron induced reactions is described in Sects.…”