Collisional angular momentum mixing of f states of Na

Abstract

In Na, the energy gap $\ensuremath{\Delta}E$ between the $n$, $d$ state and the $n$, $l>2$ states is ten times larger than $\ensuremath{\Delta}E$ between $n$, $f$ and the $n$, $l>3$ states. To investigate the effect of this difference on the $d$- and $f$-state $l$-mixing cross sections, ${\ensuremath{\sigma}}_{d}$ and ${\ensuremath{\sigma}}_{f}$, we have recently carried out experiments to measure ${\ensuremath{\sigma}}_{d\ensuremath{-}f}$, the $l$-mixing cross sections for a microwave-induced mixture of $d$ and $f$ states. Using the previously measured values of ${\ensuremath{\sigma}}_{d}$, we have derived values of ${\ensuremath{\sigma}}_{f}$ which have the same $n$ dependence as ${\ensuremath{\sigma}}_{d}$. ${\ensuremath{\sigma}}_{f}$ is larger than ${\ensuremath{\sigma}}_{d}$ for Ne, but smaller for He and Ar. In addition, we have analyzed the final states after one collision with Ar using selective field ionization of the $17l$ states and have observed that after one collision all the $l$ states are equally populated indicating that there are no $\ensuremath{\Delta}l$ selection rules for the process. This confirms the earlier suggestion that $l$ mixing is caused by a short-range interaction.