Collective vibrational states with fast iterative QRPA method

TL;DR

This paper introduces an efficient iterative QRPA method for calculating nuclear vibrational states, significantly reducing computational costs while accurately determining excitation energies and decay rates in various isotopes.

Contribution

It develops an iterative non-Hermitian Arnoldi diagonalization approach for QRPA, enabling precise calculations of nuclear states without explicit matrix storage, improving efficiency over traditional methods.

Findings

Accurately computed excitation energies of low-lying nuclear states.

Determined decay rates for selected isotopes.

Validated method across multiple isotopes and interactions.

Abstract

An iterative method we previously proposed to compute nuclear strength functions is developed to allow it to accurately calculate properties of individual nuclear states. The approach is based on the quasi-particle-random-phase approximation (QRPA) and uses an iterative non-hermitian Arnoldi diagonalization method where the QRPA matrix does not have to be explicitly calculated and stored. The method gives substantial advantages over conventional QRPA calculations with regards to the computational cost. The method is used to calculate excitation energies and decay rates of the lowest lying 2+ and 3- states in Pb, Sn, Ni and Ca isotopes using three different Skyrme interactions and a separable gaussian pairing force.