Absolute absorption on rubidium D1 line: including resonant dipole-dipole interactions

TL;DR

This study measures the absolute absorption spectra of dense rubidium vapor on the D1 line, revealing how resonant dipole-dipole interactions cause self-broadening of the linewidth, with results aligning closely with theoretical predictions.

Contribution

First precise measurement of rubidium D1 line absorption spectra accounting for dipole-dipole interactions, determining the self-broadening coefficient with high accuracy.

Findings

Self-broadening coefficient /2 = (0.69  0.04) imes 10^{-7} Hz cm^3

Absorption spectra deviation of 0.1% from theory

Linear increase of linewidth with atom density

Abstract

Here we report on measurements of the absolute absorption spectra of dense rubidium vapour on the D1 line in the weak-probe regime for temperatures up to 170 C and number densities up to 3 \times 10^14 cm^-3. In such vapours, modifications to the homogeneous linewidth of optical transitions arise due to dipole-dipole interactions between identical atoms, in superpositions of the ground and excited states. Absolute absorption spectra were recorded with deviation of 0.1% between experiment and a theory incorporating resonant dipole-dipole interactions. The manifestation of dipole-dipole interactions is a self-broadening contribution to the homogeneous linewidth, which grows linearly with number density of atoms. Analysis of the absolute absorption spectra allow us to ascertain the value of the self-broadening coefficient for the rubidium D1 line: \beta/2\pi = (0.69 \pm 0.04) \times 10^-7 Hz cm^3, in excellent agreement with the theoretical prediction.