Photoionization of $nS$ and $nD$ Rydberg atoms of Rb and Cs from the near-infrared to the ultraviolet spectral region

TL;DR

This paper calculates photoionization cross sections for rubidium and cesium Rydberg atoms across a broad spectral range, identifying minima due to Cooper effects and shape resonances, with implications for atomic physics and applications.

Contribution

It provides detailed calculations of photoionization cross sections for Rb and Cs Rydberg atoms from infrared to ultraviolet, highlighting the origins of PI minima and proposing experimental measurement methods.

Findings

Identification of broad Cooper minima in $nS$ channels.

Detection of narrow shape resonance minima in $nD$ channels.

Discussion of implications for atomic physics and practical applications.

Abstract

We present calculations of the photoionization (PI) cross sections of rubidium and cesium Rydberg atoms for light with wavelengths ranging from the infrared to the ultraviolet, using model potentials from [M. Marinescu, H. R. Sadeghpour, and A. Dalgarno, Phys. Rev. A 49, 982 (1994)]. The origins of pronounced PI minima are identified by investigating the free-electron wavefunctions. These include broad PI minima in the $nS$ to $\epsilon P$ PI channels of both Rb and Cs, with free-electron energy $\epsilon$, which are identified as Cooper minima. Much narrower PI minima in the $nD$ to $\epsilon F$ channels are due to shape resonances of the free-electron states. We describe possible experimental procedures for measuring the PI minima, and we discuss their implications in fundamental atomic physics as well as in practical applications.