Study of the gamma Deexcitation Process of Highly Excited Nuclear States

摘要

The purpose of this thesis is to provide a description of the gamma-ray deexcitation process of highly excited nuclear states, formed in nuclear reactions. Because different reactions differ only in the way in which the highly excited states are initially populated, the calculations presented here can generally be applied to any reaction, provided that the initial population is properly chosen. The new feature of this calculation is the explicit separation of the total density of states in two pieces: a discrete part which is treated explicitly and a continuum part which is treated statistically. Two different reactions have been studied, viz. low energy neutron capture reactions and (H.I., xn gamma )-reactions. It is shown that the deexcitation process of a set of excited nuclear levels by means of gamma-ray emission is equivalent to a master equation system. After a more general introduction to master equation systems a master equation technique for the calculation of gamma-ray spectra and the analysis of feeding times in nuclear reactions is presented. This technique, combined with a cascade technique, is then applied to (n, gamma )- and (H.I., xn gamma )-reactions in the remainder of the thesis. Results of calculations for the case of thermal neutron capture on exp 149 Sm are compared to experimental data. (H.I., xn gamma )-reactions are then discussed. Results of calculations for exp 150 Nd( alpha , 4n) exp 150 Sm, exp 158 Gd( alpha , 4n) exp 158 Dy and exp 160 Gd( alpha , 4n) exp 160 Dy are compared to experimental data. (Atomindex citation 10:443657)