Noble-gas-induced broadening of transitions to RydbergSandDstates in atomic sodium

Abstract

We have made comprehensive measurements of the noble-gas-induced (He, Ne, Ar, Kr, and Xe) broadening cross sections of the Na $3S-nS$ ($3S-nD$) transitions, from $n=5\mathrm{} \mathrm{to} 38$ ($n=4\mathrm{} \mathrm{to} 40$). These measurements were made using the trilevel-echo technique and are an extension and refinement of our earlier work. We find that the cross sections increase as the geometric cross section at low values of $n$, and then, at a value of $n$ which depends on the particular noble gas, begin to decrease and eventually reach an asymptotic value at high $n$. The broadening cross sections for the nearly degenerate $D$ states are significantly larger than those for the $S$ states and clearly show the effect of $l$-changing collisions. We also compare our measured $S$-state broadening cross sections with the cross sections calculated using the theory of Omont and find good qualitative agreement.