Observation of the nuclear magnetic octupole moment of $^{173}$Yb from precise measurements of hyperfine structure in the ${^3P}_2$ state

TL;DR

This paper reports precise measurements of hyperfine structure in $^{173}$Yb's ${^3P}_2$ state, leading to the first extraction of its nuclear magnetic octupole moment with significantly improved accuracy.

Contribution

The study provides the first measurement of the nuclear magnetic octupole moment of $^{173}$Yb using hyperfine structure analysis with unprecedented precision.

Findings

Hyperfine coefficients A and B measured with 200 kHz precision

Nuclear magnetic octupole moment $oxed{ ext{Ω}=-34.4(21)}$ b·μ_N extracted

Second-order corrections are below 30 kHz

Abstract

We measure hyperfine structure in the metastable ${^3P}_2$ state of $^{173}$Yb and extract the nuclear magnetic octupole moment. We populate the state using dipole-allowed transitions through the ${^3P}_1$ and ${^3S}_1$ states. We measure frequencies of hyperfine transitions of the ${^3P}_2 \rightarrow {^3S}_1$ line at 770 nm using a Rb-stabilized ring cavity resonator with a precision of 200 kHz. Second-order corrections due to perturbations from the nearby ${^3P}_1$ and ${^1P}_1$ states are below 30 kHz. We obtain the hyperfine coefficients as: $A=-742.11(2)$ MHz, $B=1339.2(2)$ MHz, which represent two orders-of-magnitude improvement in precision, and $C=0.54(2)$ MHz. From atomic structure calculations, we obtain the nuclear moments: quadrupole $Q=2.46(12)$ b and octupole $\Omega=-34.4(21)$ b\,$\times \mu_N$.