Study of the dissociative recombination in xenon following (2+1) multiphoton ionisation

Vacuum ultraviolet emissions of xenon were investigated at room temperature following two-photon selective excitation of the first metastable state Xe(³P₂) and (2+1) multiphoton ionization (MPI) via the Xe(³P₂) relay state, in pure xenon. For the 2-photon selective excitation of the lowest metastable state of xenon, a brief (7 ns) and rather low intensity (I < 10⁷ W.cm^-2) incident laser was used. In order to achieve (2+1) MPI the same laser was used, but at much higher intensity (I > 10⁹ W.cm^-2). A kinetic analysis of the VUV emission of the second continuum at 172 nm was performed, comparing the temporal dependence of the radiation characteristics consecutive to selectively populating the metastable state or following MPI of xenon. At high laser energy a slow non exponential component appeared in the time-dependent decay of the VUV luminescence. The influence of pressure on this slow component was analysed for xenon pressures ranging from 100 Torr to 600 Torr. Our observations are consistent with the production of Xe (6s) states after a dissociative recombination of Xe²⁺ ions.