Spectroscopy of high pressure rubidium-noble gas mixtures

TL;DR

This paper reports on high-pressure spectroscopy of rubidium-noble gas mixtures, demonstrating spectral scaling, and observing laser cooling effects in a controlled laboratory setup at extreme conditions.

Contribution

It presents novel spectroscopic measurements of dense rubidium-noble gas mixtures at high pressures and temperatures, including observations of redistributional laser cooling.

Findings

Spectra follow Kennard-Stepanov frequency scaling.

Successful observation of redistributional laser cooling.

Spectroscopy conducted at pressures up to 250 bar and 500 K.

Abstract

Spectroscopy of alkali-buffer gas mixtures at high pressures from single-digit to several 100 bars in the regime of substantial collisional broadening is relevant in a wide range of fields, ranging from collisional redistribution cooling to laboratory astrophysics. Here we report on spectroscopic measurements of dense rubidium-noble gas mixtures recorded in a pressure cell equipped with soldered sapphire optical viewports, which allows for the controlled realization of extreme conditions of high temperature and high pressure in a table top laboratory experiment. In the gas cell, we have recorded absorption and emission spectra of rubidium subject to 250 bar helium buffer gas pressure at 500 K temperature. The spectra to good accuracy fulfill the thermodynamic Kennard- Stepanov frequency scaling of the ratio of absorption and emission spectral profiles. Further, the long optical path length in the cell allowed to both record spectra of rubidium-argon mixtures at moderate temperatures and high pressures and to observe redistributional laser cooling in this system.