Precise measurement of hyperfine structure in the ${2P}_{1/2}$ state of $^{7}$Li using saturated-absorption spectroscopy

TL;DR

This paper presents a highly precise measurement of the hyperfine structure in the ${2P}_{1/2}$ state of $^{7}$Li using saturated-absorption spectroscopy, providing data that challenges existing theoretical models.

Contribution

It reports a new, more accurate measurement of the hyperfine interval in $^{7}$Li's ${2P}_{1/2}$ state, and compares it with previous data and theoretical predictions.

Findings

Measured hyperfine interval: 92.040(6) MHz

Magnetic dipole constant A: 46.047(3) MHz

Discrepancy with theoretical calculations >80 kHz

Abstract

We report a precise measurement of the hyperfine interval in the ${2P}_{1/2}$ state of $^{7}$Li. The transition from the ground state ($D_1$ line) is accessed using a diode laser and the technique of saturated-absorption spectroscopy in hot Li vapor. The interval is measured by locking an acousto-optic modulator to the frequency difference between the two hyperfine peaks. The measured interval of 92.040(6)~MHz is consistent with an earlier measurement reported by us using an atomic-beam spectrometer [Das and Natarajan, J.\ Phys.\ B {\bf 41}, 035001 (2008)]. The interval yields the magnetic dipole constant in the $P_{1/2}$ state as $A=46.047(3)$, which is discrepant from theoretical calculations by $>80$~kHz.