Selection rule for fragmentations of doorway s-hole states in light nuclei.

Abstract

A selection rule for fragmentations of doorway {ital s}-hole states in light nuclei is given. In the two-body fragmentation process of the doorway {ital s}-hole states in light nuclei, smaller fragments than the {alpha} particle ({ital p}, {ital n}, {ital d}, {ital t}, and {sup 3}He) are allowed, while the fragments such as the {alpha} particle and the larger particles are forbidden, in spite of the fact that the {ital Q} value for the {alpha} fragment is similar to or even larger than those for the {ital p}, {ital n}, and {ital d} fragments. The selection rule comes from the spatial symmetry of the doorway {ital s}-hole states. The spectroscopic factors and partial widths for the two-body fragmentations of the {ital s}-hole state of {sup 11}B and {sup 15}N are calculated to show the selection rule. The calculated escape widths for the {sup 11}B({ital s}-hole) and {sup 15}N({ital s}-hole) doorway states are in good correspondence with the experimental widths. This may suggest that the following scenario is realized; in light nuclei the fragmentation process of the {ital s}-hole state in the doorway stage is superior or competitive to that in the compound nuclear stage. {copyright} {ital 1996 The American Physicalmore » Society.}« less