Associative ionization in collisions between twoNa(3P)atoms

Abstract

We have measured the rate coefficient [$k=5.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{3}$/s (\ifmmode\pm\else\textpm\fi{}37%)] for associative ionization occurring in collisions between two $\mathrm{Na}(3P)$ atoms, by measuring the current resulting from excitation of Na vapor by cw-laser radiation. The major source of uncertainty in measurements of this type is in the determination of the number density and spatial distribution of excited atoms. Here we have measured the excited-atom density by three methods, and we have studied the spatial distribution of excited atoms in detail. Our rate coefficient at $T\ensuremath{\sim}650$ K is compared to other experimental results.