Effect of the Tensor Force on Charge-Exchange Spin-Dependent Multipole Excitations

The charge-exchange spin-dipole (SD) and spin-quadrupole (SQ) strength functions of Zr-90 are calculated with and without the tensor terms of the Skyrme interaction in self-consistent HF+RPA approach. It is found that, in SD and SQ transitions, the RPA correlations associated with the tensor terms shift dramatically the strengths of (Y-iota sigma)lambda = iota-1 and (Y-iota sigma)(lambda)=iota modes upward and downward, respectively, and also shift the strengths of (Y iota sigma)(lambda=iota+1) modes upward. The coupling between (Y iota=lambda-1 sigma)(lambda) and (Y iota=lambda+1 sigma)(lambda) modes arising from the tensor correlation is noticeable. The RPA tensor correlations produce strengths of SD and SQ modes, which are distributed in a much wider energy range, and the (Y-iota sigma)(lambda=iota-1) modes dominate the high energy part of the strength functions. These energy shifts and coupling effects of different modes can be understood qualitatively by expressing a finite range tensor force in a separable form.