Influence of multiphoton ionization on frequency conversion in alkali metal vapors

An investigation was made of tunable emission of violet radiation from alkali metal vapors involving a fourphoton process using radiation from a single tunable laser. The influence of ionization of the atoms on the parameters of the emitted radiation was also studied. It was established that as the vapor pressure increases, efficient collisional ionization is observed in addition to resonant three-photon ionization and this may result in complete ionization of the atoms.