Multiphoton ionization of Xe and several small molecules at 193 and 248 nm

Abstract

Relative multiphoton ionization rates for Xe, NO, NO 2, N 2O, O 2, N 2, CO, CO 2, H 2O, SO 2, CF 3Cl, CF 3I, and C 2F 5I have been measured as a function of laser power at 193 and 248 nm. A weakly focused rare-gas—halogen excimer laser beam passes in front of the exit aperture of an ion drift tube, and ions formed in the laser beam are extracted by the drift field into a quadrupole mass spectrometer. Relative ionization rates varied among these molecules by more than six orders of magnitude. In several cases the ionization mechanism could be inferred from the ion fragmentation pattern, a knowledge of the single-photon spectroscopy of the molecule, and the power dependence of the ionization rate.