VUV laser photoionization of laser-stimulated desorbed species

We report here first results about single-photon VUV laser photoionization of desorbed species from a silicon surface irradiated by a pulsed and tunab le UV laser (290-300 nm). The combination of VUV photoionization at 10 eV w ith laser-induced surface desorption offers a largely non-destructive and s ensitive method for quantitative analysis. Indeed it allows mass spectromet ry measurements with uniform sensitivity and without breaking the chemical bonds in the probed species. The energy of the VUV photons (9.91 eV) is abo ve the ionization limits of a number of molecules and fragments. Moreover, adjustment of the delay between the desorbing and the probe lasers allows t he measurement of the time-of- flight distribution of the ejected species. Data extracted from these measurements are fundamental for a better underst anding of laser-surface interaction phenomena.