Ionization of Rydberg atoms by blackbody radiation

TL;DR

This study provides detailed theoretical calculations of blackbody radiation-induced ionization rates in alkali-metal Rydberg atoms, considering population redistribution and electric field effects, with experimental comparisons and practical formulas for estimations.

Contribution

It introduces comprehensive calculations of BBR ionization rates for various alkali Rydberg states, including redistribution effects and a Cooper minimum, validated against experimental data.

Findings

Good agreement with experimental data for Na Rydberg states

Identification of a Cooper minimum in Li Rydberg transitions

Analytical formulas for estimating BBR ionization rates

Abstract

We have studied an ionization of alkali-metal Rydberg atoms by blackbody radiation (BBR). The results of the theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. Calculations have been performed for nS, nP and nD states which are commonly used in a variety of experiments, at principal quantum numbers n=8-65 and at the three ambient temperatures of 77, 300 and 600 K. A peculiarity of our calculations is that we take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n. A Cooper minimum for BBR-induced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8-20 at 300 K. A good agreement for all states except nS with n>15 is observed. Useful analytical formulas for quick estimation of BBR ionization rates of Rydberg atoms are presented. Application of BBR-induced ionization signal to measurements of collisional ionization rates is demonstrated.