Hyperfine structure of the $2\,^3\!P$ state in $^9$Be and the nuclear quadrupole moment

TL;DR

This study accurately calculates the hyperfine structure of the $2^3P$ state in $^9$Be, incorporating various physical effects, and determines a highly precise nuclear quadrupole moment that challenges previous measurements.

Contribution

The paper presents the most precise calculation of the $^9$Be nuclear quadrupole moment using advanced methods and compares it with experimental data.

Findings

Determined $Q_N = 0.05350(14)$ barns for $^9$Be.

Discrepancy with previous quadrupole moment measurements.

Enhanced understanding of hyperfine interactions in $^9$Be.

Abstract

We have performed accurate calculations of the hyperfine structure of the $2\,^3\!P$ state in the $^9$Be atom with the help of highly optimized, explicitly correlated functions, accounting for the leading finite nuclear mass, radiative, nuclear structure and relativistic effects. By comparison with measurements, we have determined the $^9$Be nuclear quadrupole moment to be $Q_{\rm N} = 0.05350(14)$ barns, which is not only the most accurate result, but also disagrees with previous determinations.