James J. Hogan

Isomer ratios of Tc isotopes produced in 10–65 MeV bombardments of 96Mo

Abstract Cross-sections and isomer ratios have been measured for three related nuclear reactions over the proton bombarding energy region from 10–65 MeV. The ( p , 2–4 n ) reactions on enriched 96 Mo produce the isomericairs 93 Tc m,g , 94 Tc m,g and 95 Tc m,g . Experimental results are discussed and interpreted in terms of the changing production mechanism for the reactions over this range of bombarding energies.

Study of the 141Pr(p,xn) reaction from 10–85 MeV

Abstract Excitation functions for the production of the 141 Pr( p,xn ) 142−χ Nd nuclear reactions for proton bombarding energies ranging from 10–85 MeV have been measured. These experimental results have been compared to excitation functions calculated by the two models of the most widely used intranuclear cascade calculation. Strengths and deficiencies of both models are discussed, with particular reference to their sensitivity to capture of the impinging proton. Special emphasis is given to calculation of the production of the two isomers of 139 Nd.

The 96Mo(p, n) 96Tcm,g reaction from 10 to 65 MeV

Abstract The production cross sections and isomer ratios of the 4+ and 7+ states of 96Tc produced from 10–65 MeV proton bombardment of 96Mo have been measured. Results show an enormous variation-nearly three orders of magnitude-in the ratio σ m σ g . In the compound nucleus mechanism region, the results are explainable in terms of the unusually large spins of both isomers. To date, the (p, n) results arising in the bombarding energy region where direct mechanisms predominate are unexplained.

The pre-equilibrium statistical model: Comparison of calculation with two (p, xn) reactions

Abstract Calculations of excitation functions have been made and compared with experiment for the 75As(p, n) and (p, 3n) reactions and for 96Mo(p, xn), x = 1−4, reactions from 10 to 85 MeV. The most recent VPOT version of the Vegas Intranuclear Cascade and the EVA-HYB version of the Pre-Equilibrium Statistical Model have been used. The EVA-HYB results provide excellent fits to the six excitation functions with a single set of parameters, while the VPOT calculation in general was unsuccessful in the prediction of both the peak cross sections and in the energy dependence of the high energy tails.

An evaluation of alpha particle clustering in heavy nuclei

In recent years, the pre-equilibrium models of nuclear reactions have been used to analyze many experiments involving the emission of alpha particles. The results of these analyses have been used as the basis for a calculation of the extent of alpha particle clustering in heavy nuclei. Calculations are presented of the rate of nucleon-nucleon and nucleon-alpha interactions in nuclear matter. Normalizing these to the preformation factors found in reaction studies, the number of alpha clusters in several complex nuclei has been obtained. It is suggested that the number of such preformed alpha clusters in nuclei havingA=50, 90, 141, 202, and 232 are, respectively, 2.1, 3.6, 5.2, 6.9, and 7.8.

Decay of the complete fusion nucleus,151Eu

Excitation functions have been measured for the133Cs(13O, 3–6n)145–148Eu reactions at incident energies from 75 to 125 MeV and compared to those previously reported for the139La(12C, 3–6n) reaction system with the same complete fusion nucleus,151Eu. The semiclassical Diamond-Stephens approach to the treatment of angular momentum in evaporative processes is extended and a method for extraction of the moment of inertia, the critical value of angular momentum for fusion, and the yrast line for151Eu is presented. The model is then used to predict the excitation functions and the results are compared to experiment.

Alpha particle clusters in complex nuclei: a semi‐empirical calculation

Using results of pre-equilibrium model simulations of complex nuclear reactions on several targets, a scattering calculation was developed which may be used to determine the extent of alpha particle clustering in nuclei with A > 40. Results, showing the effect of various assumptions, are discussed. 2 references.