Field ionization of highly excited states of sodium

Abstract

We have observed the selective ionization of the degenerate $|{m}_{j}|$ levels of $s$, $p$, and $d$ states of sodium in the range of $n$ from 15 to 20 and have shown that atoms produced in these low-field (\ensuremath{\sim} 10 V/cm) states pass adiabatically from low-field $|{m}_{j}|$ to intermediate-field $|{m}_{l}|$ states. Experiments on the Stark manifold states in intermediate fields (\ensuremath{\sim} 1 kV/cm) and high fields (\ensuremath{\sim} 4 kV/cm) show that the $|{m}_{l}|=0 \mathrm{and} 1$ states pass adiabatically from intermediate- to high-field states and that the passage of the $|{m}_{l}|=2$ states is very nearly adiabatic. These findings suggest a general approach for predicting the threshold fields for ionization of atomic Rydberg states.