APPLICATIONS OF STATISTICAL NUCLEAR-PHYSICS TO NUCLEAR SPECTROSCOPY

A number of new results pertaining to properties of complex nuclear spectra are given and illustrated with data from many experiments. We are concerned with the situation in which a group of closely spaced - though, in principle, still resolvable - nuclear levels is observed, and use the statistical model to interpret the properties of the corresponding particle and photon spectra. According to this model, the physics information contained locally in such a spectrum may be expressed in terms of a small number of average quantities: level spacings and reduced partial widths. The local fine structure, on the other hand, remains unpredictable ("chaotic") but is governed by universal statistical laws. Experimental examples are taken from charged-particle and gamma-ray spectra following the beta decay of far-unstable nuclei and from (e, e') reactions studied by high-resolution methods. We discuss (i) the determination of level densities, (ii) the role of fluctuation corrections in the interpretation of branching ratios and resonance lifetimes, and finally (iii) how Monte Carlo simulations of complex spectra may serve to test sensitivity and experimental bias. © 1990.