N. Frazier et al., STRENGTH FUNCTIONS AND SPREADING WIDTHS OF SIMPLE SHELL-MODEL CONFIGURATIONS, Physical review. C. Nuclear physics, 54(4), 1996, pp. 1665-1674
The exact solution of the many-body problem in the framework of the nu
clear shell model with a realistic residual Hamiltonian makes it possi
ble to study the fragmentation of simple configurations as a function
of excitation energy and interaction strength. The analysis is perform
ed for 839 states with quantum numbers J pi T = 0(+)0 in a system of 1
2 valence particles within the sd shell. Our statistics allow us to es
tablish the generic shape of the strength function in the region of st
rong mixing. For the realistic interaction, the strength function is c
lose to Gaussian in the central part and has exponential wings. The sp
reading width is larger than predicted by the standard golden rule. At
the artificially suppressed interaction strength, we recover the Brei
t-Wigner shape and the golden rule for the spreading width. The transi
tion between these regimes agrees with theoretical considerations base
d on the idea of chaotic dynamics.