Low-Lying States in Odd-Mass Nuclei and the Extended Random Phase Approximation

Abstract. The Quasi-particle Random Phase Approximation (QRPA) is known to be inade-quate for describing the vibrational states in even-even nuclei far from the valley of stability. An extended version of this theory (ERPA) proved successful in removing some deficiencies of the QRPA. Within the ERPA we derived renormalized interaction strengths between an even-even core and a particle outside of that core in odd-mass nuclei. The problem of investigating the properties of odd-mass nuclei within this approach is essentially reduced to solving a large system of coupled non-linear equations which takes into account the pairing correlations, the multipole-multipole interaction and the core-particle coupling.