G. Stratan’s research while affiliated with Joint Institute for Nuclear Research and other places

A method for separating the centre-of-mass motion of a two or more particle cluster is developed. This method works for an arbitrary central shell model potential. Only the internal motion wave function must be previously defined. Formulas are obtained for the case of clusters with arbitrary angular momenta of the internal motion and with constituent particles of unequal masses. The problem of separating the relative motion of a pair of particles with previously defined centre-of-mass motion is also solved. As a byproduct, is useful integral formula for generalized Talmi-Moshinsky coefficients is obtained. Some applications of the method are demonstrated in calculating the overlap interests to radioactive states, the form factors for direct x-transfer reactions and the two-parties interaction matrix elements.

Recently some important results have been obtained in calculating absolute alpha-decay widths, the calculations having been performed in the zero range alpha-particle approximation. In this paper the effects of the finite size of the alpha-particle are considered. Two important effects have been found: (i) for the finite size calculation, the absolute alpha-decay widths decrease by 2-3 orders of magnitude, and (ii) the finite size effects are strongly dependent on the shell model configuration of the initial nucleus. In the framework of the superfluid model the absolute probabilities of finite size alpha-particle emission have been calculated for the favored alpha-transitions of more than 200 spherical nuclei. The theoretical alpha-widths turn out to be smaller than the experimental ones by a factor of 10, which is approximately constant for all the nuclei studied.