Elimination of spurious modes before the solution of quasiparticle random-phase-approximation equations

Abstract

A general method for the elimination of the spurious admixtures (SA) from two-quasiparticle (2qp) intrinsic nuclear excitations is proposed. It assumes the construction of 2qp configuration space with elements orthogonal to the given spurious mode. The method exploits Quasiparticle-Random-Phase-Approximation (QRPA) matrices but does not need a prior numerical solution of QRPA, i.e. SA-elimination occurs before QRPA equations are solved. After the refined basis is prepared, it can be used in the given matrix QRPA. The method is suitable for any type of spurious modes. We demonstrate the efficiency of the method for QRPA in axially deformed 154Sm . The cases of SA arising from the center of mass motion ($ K^{\pi}=0^{-} , 1^{-}$ states), nuclear rotation ($ K^{\pi}=1^+$ states), and pairing-induced violation of the particle number ($ K^{\pi}=0^{+}$ states) are considered. The method is compared with other SA-elimination schemes.