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

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 $6D\to 7F$ 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 $7P$ fine and hyperfine structure. We show that $7P$ 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.

accepted for publication in Journal of Physics B: Atomic, Molecular and Optical Physics