Velocity preserving transfer between highly excited atomic states: Black Body Radiation and Collisions

TL;DR

This study investigates how black body radiation and atomic collisions redistribute excitation among cesium atoms, enabling high-resolution and sub-Doppler spectroscopy of highly excited states while preserving atomic velocities.

Contribution

It demonstrates velocity-preserving excitation transfer mechanisms via BBR and collisions, facilitating advanced spectroscopic techniques in dense alkali vapors.

Findings

BBR induces velocity-preserving excitation redistribution at low densities.

Interatomic collisions cause state-changing, velocity-preserving excitation redistribution at high densities.

Mechanisms are relevant for high-lying excited state experiments in dense alkali vapors.

Abstract

We study the excitation redistribution from cesium $7\mathrm{P}_{1/2}$ or $7\mathrm{P}_{3/2}$ to neighboring energy levels by Black Body Radiation (BBR) and inter atomic collisions using pump-probe spectroscopy inside a vapor cell. At low vapor densities we measure redistribution of the initial, velocity-selected, atomic excitation by BBR. This preserves the selected atomic velocities allowing us to perform high resolution spectroscopy of the $\mathrm{6D\rightarrow 7F}$ transitions. This transfer mechanism could also be used to perform sub-Doppler spectroscopy of the cesium highly-excited $\mathrm{nG}$ levels. At high densities we observe interatomic collisions redistributing the excitation within the cesium $\mathrm{7P}$ fine and hyperfine structure. We show that $\mathrm{7P}$ redistribution involves state-changing collisions that preserve the initial selection of atomic velocities. These redistribution mechanisms can be of importance for experiments probing high lying excited states in dense alkali vapor.