Absolute absorption on the rubidium D₁line including resonant dipole–dipole interactions

Abstract

Here we report on measurements of the absolute absorption spectra of dense\nrubidium vapour on the D1 line in the weak-probe regime for temperatures up to\n170 C and number densities up to 3 \\times 10^14 cm^-3. In such vapours,\nmodifications to the homogeneous linewidth of optical transitions arise due to\ndipole-dipole interactions between identical atoms, in superpositions of the\nground and excited states. Absolute absorption spectra were recorded with\ndeviation of 0.1% between experiment and a theory incorporating resonant\ndipole-dipole interactions. The manifestation of dipole-dipole interactions is\na self-broadening contribution to the homogeneous linewidth, which grows\nlinearly with number density of atoms. Analysis of the absolute absorption\nspectra allow us to ascertain the value of the self-broadening coefficient for\nthe rubidium D1 line: \\beta/2\\pi = (0.69 \\pm 0.04) \\times 10^-7 Hz cm^3, in\nexcellent agreement with the theoretical prediction.\n