Alpha strength factors in medium nuclei

Abstract

Alpha strength factors are calculated for use in heavy-ion induced α-transfer reactions and in (α, p) reactions on medium nuclei. Detailed calculations are performed in a weak coupling shell model to study the distribution of α-strength over the nuclear states and to explore the α-clustering amplitudes of j- j coupled basis states. Alpha clustering in a model space with states of good isospin as well as states described in neutron-proton formalism is discussed. It is found that the α-cluster strength contained in the configurations (pf) 4, (sd) 4, (pf) 3(sd) 1 and (pf) 1(sd) 3 fragments among several or many states. For the (pf) 2(sd) 2 configuration, conversely, most of the α-strength exists in the lowest state of the configuration, and such states form a band of positive parity states which exhibits rotational properties. A brief comparison with (α, p) and 54Fe ( 16O, 12C) 58Ni experiments is made. The α-transfer probability was calculated in a semiclassical model. The effects of correlations which produce enhancements of factors of ten are essential to explain observed enhancements in the α-strengths. Alpha strength factors for the (sd) 4 configurations for nuclei in the Zr region are also given.