Exponential increase of energy level density in atoms: Th and Th II

TL;DR

This paper demonstrates that the energy level density in open-shell atoms like Th and Th II increases exponentially with excitation energy, with implications for nuclear clock development.

Contribution

It provides analytical estimates and numerical calculations of energy level density increase in Th and Th II atoms, relevant for nuclear transition studies.

Findings

Energy level density increases exponentially with excitation energy.

Relativistic Hartree-Fock and configuration interaction methods used.

Implications for electron effects on nuclear transitions in clocks.

Abstract

We present analytical estimates and numerical calculations showing that the energy level density in open-shell atoms increases exponentially with increase of excitation energy. As an example, we use the relativistic Hartree-Fock and configuration interaction methods to calculate the density of states of Th and Th II. The result is used to estimate the effect of electrons on the nuclear transition which is considered for the use in a nuclear clock.