Nuclear-spin-related properties of~the dual-frequency Doppler-free resonance

TL;DR

This paper analyzes the properties of dual-frequency Doppler-free resonances in alkali-metal atoms, revealing how nuclear spin influences resonance width and absorption, supported by experimental results with rubidium and cesium.

Contribution

It provides a theoretical framework for understanding nuclear-spin effects on Doppler-free resonances and confirms predictions through experiments with specific alkali-metal isotopes.

Findings

Absence of optical pumping at the crossover center with parallel polarizations.

Increase in absorption at the peak center for I=I-1/2.

Reduced resonance width with two-photon detuning in orthogonal polarizations.

Abstract

We investigate the dual-frequency Doppler-free resonance in the D1 line of alkali-metal atoms for any accessible value of the nuclear spin I. The consideration is performed using the symmetries of the dipole operator and the basis, where the quantization axis is directed along the polarization of the one of optical waves. We show that there is the absence of the optical pumping in the scheme with parallel polarizations for the center of the crossover, resulting in its smallest width. Secondly, the growth in the absorption for the center of the peak with Fe=I-1/2 and the decrease of its width with the two-photon detuning in the case of~orthogonal polarizations is explained. Particular attention is paid to the special case of I=3/2, where this effect is the most pronounced. The experiment with 87Rb, 85Rb, and 133Cs atoms is in agreement with the analysis.