Strong enhancement of level densities in the crossover from spherical to deformed neodymium isotopes

Abstract

Understanding the evolution of level densities in the crossover from spherical to well-deformed nuclei has been a long-standing problem in nuclear physics. We measure nuclear level densities for a chain of neodymium isotopes ${}^{142,144-151}$Nd which exhibit such a crossover. These results represent to date the most complete data set of nuclear level densities for an isotopic chain between neutron shell-closure and towards mid-shell. We observe a strong increase of the level densities along the chain with an overall increase by a factor of $\approx 170$ at an excitation energy of 7.5 MeV and saturation around mass 150. Level densities calculated by the shell model Monte Carlo (SMMC) are in excellent agreement with these experimental results. Based on our experimental and theoretical findings, we offer an explanation of the observed mass dependence of the level densities in terms of the intrinsic single-particle level density and the collective enhancement.

7 pages, 4 figures

References in corpus (6)

• The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries
• Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities
• The SiRi Particle-Telescope System
• 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
• Statistical properties of the well deformed ${}^{153,155}$Sm nuclei and the scissors resonance

Cited by in corpus (6)

• Statistical properties of the well deformed ${}^{153,155}$Sm nuclei and the scissors resonance
• Broken axial symmetry as essential feature for a consistent modelling of various observables in heavy nuclei
• Experimental Evidence of Large Collective Enhancement of Nuclear Level Density and its Significance in Radiative Neutron Capture
• Microscopic-macroscopic level densities for low excitation energies
• Deviations from the Porter-Thomas Distribution due to Nonstatistical $\gamma$ Decay below the ${}^{150}$Nd Neutron Separation Threshold
• Nuclear level densities away from line of $\beta$-stability