Ionization of sodium and rubidiumnS,nP, andnDRydberg atoms by blackbody radiation

Abstract

Results of theoretical calculations of ionization rates of Rb and Na Rydberg atoms by blackbody radiation (BBR) are presented. Calculations have been performed for $nS$, $nP$, and $nD$ states of Na and Rb, which are commonly used in a variety of experiments, at principal quantum numbers $n=8--65$ and at three ambient temperatures of 77, 300, and $600\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. 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 $n$. The calculated ionization rates are compared with the results of our earlier measurements of BBR-induced ionization rates of Na $nS$ and $nD$ Rydberg states with $n=8--20$ at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A good agreement for all states except $nS$ with $n>15$ is observed. We also present the useful analytical formulas for the quick estimation of BBR ionization rates of Rydberg atoms.