Continuum gamma rays following (HI, xnγ) reactions

The continuum gamma-ray spectrum following neutron emission in a (HI, xngamma) reaction consists of two parts: a high-energy component whose intensity decreases exponentially with gamma-energy, the initial statistical cascade; and a low-energy bump which usually contains most of the intensity and consists predominantly of stretched E2 transitions, the yrast cascade. The latter cascade carries away most of the angular momentum of the product nucleus, and so there is a good correlation between the average angular momentum of the initial compound nucleus leading to a particular product and the average gamma-ray multiplicity in that reaction. The measured values of the gamma-ray multiplicity show a variation of a factor of ten and have dependencies on the projectile mass and energy which can be explained with simple considerations. Determination of the moment-of-inertia of the nucleus at spins as high as 60h/2π involves difficulties and is not yet accurate, but is very interesting to do and seems possible of better accuracy. (1 table, 16 figures)