Off-resonance production of ions in laser-excited sodium vapor.

Abstract

The production of ${\mathrm{Na}}^{+}$ and ${\mathrm{Na}}_{2}$${\mathrm{}}^{+}$ in sodium vapor irradiated by pulsed laser light in the D-line region of the spectrum has been studied by varying the laser power density and the wavelength. The data, which were acquired with an order-of-magnitude higher resolution than those in our previous experiments, support our earlier conclusion that ions formed at laser wavelengths close to, but not coincident with, the D lines result from three-photon resonance-enhanced ionization of ${\mathrm{Na}}_{2}$ molecules present in the vapor.