Spectroscopy of atomic rubidium at500−barbuffer gas pressure: Approaching the thermal equilibrium of dressed atom-light states

Abstract

We have recorded fluorescence spectra of the atomic rubidium D-lines in the presence of several hundreds of bars of buffer gas pressure. The large collisional broadening of this system interpolates between usual atomic physics gas phase and solid-liquid phase conditions. In our buffer gas cell, with additional saturation broadening, a spectral linewidth comparable to the thermal energy of the atoms in the cell is achieved. An observed intensity-dependent blue asymmetry of the spectra is interpreted as evidence for the onset of thermal equilibrium of dressed atom-light states.