Nuclear deformation in the laboratory frame

Abstract

We develop a formalism for calculating the distribution of the axial quadrupole operator in the laboratory frame within the rotationally invariant framework of the configuration-interaction shell model. The calculation is carried out using a finite-temperature auxiliary-field quantum Monte Carlo method. We apply this formalism to isotope chains of even-mass samarium and neodymium nuclei, and show that the quadrupole distribution provides a model-independent signature of nuclear deformation. Two technical advances are described that greatly facilitate the calculations. The first is to exploit the rotational invariance of the underlying Hamiltonian to reduce the statistical fluctuations in the Monte Carlo calculations. The second is to determine quadruple invariants from the distribution of the axial quadrupole operator. This allows us to extract effective values of the intrinsic quadrupole shape parameters without invoking an intrinsic frame or a mean-field approximation.

12 pages, 8 figures, and 1 table. Added two references; minor changes in the text

References in corpus (5)

• Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities
• Heavy deformed nuclei in the shell model Monte Carlo method
• Crossover from vibrational to rotational collectivity in heavy nuclei in the shell-model Monte Carlo approach
• Shell model based deformation analysis of light Cadmium isotopes
• Nuclear deformation at finite temperature