Nuclear Level Density of161Dy in the Shell Model Monte Carlo Method

C Özen,H Nakada,Y Alhassid

doi:10.1051/epjconf/20122105002

Abstract

We extend the shell-model Monte Carlo applications to the rare-earth region to include the odd-even nucleus ${}^{161}$Dy. The projection on an odd number of particles leads to a sign problem at low temperatures making it impractical to extract the ground-state energy in direct calculations. We use level counting data at low energies and neutron resonance data to extract the shell model ground-state energy to good precision. We then calculate the level density of ${}^{161}$Dy and find it in very good agreement with the level density extracted from experimental data.

Highlights

The shell model Monte Carlo (SMMC) [1,2,3,4] is a powerful method for the calculation of statistical properties of nuclei at finite temperature
The projection on an odd number of particles leads to a sign problem, making it impractical to calculate thermal observables at low temperatures
Because of the sign problem introduced by the projection on an odd number of particles, the thermal energy E(β) of 161Dy can in practice be calculated only up to β ∼ 5.5 MeV−1

Summary

Introduction

The shell model Monte Carlo (SMMC) [1,2,3,4] is a powerful method for the calculation of statistical properties of nuclei at finite temperature. This approach has proven to be useful in the calculation of nuclear level densities [5,6,7,8,9]. We extend the application of SMMC in rare-earth nuclei to include the odd-even nucleus 161Dy. The projection on an odd number of particles leads to a sign problem (even for good-sign interactions), making it impractical to calculate thermal observables at low temperatures. We calculate the SMMC level density of 161Dy and compare it with the level density extracted from available data

Choice of Model Space and Interaction

Ground-state Energy

Level Density

Conclusions