IR laser ionization of H 2O, D 2O, CH 3OH, and CH 3CN samples of varied thickness condensed on a metal surface

Abstract

CO 2 laser-induced desorption and ionization processes are studied in a UHV apparatus employing a quadrupole mass spectrometer without ion source. Mass spectra are recorded for very thin and macroscopic sample layers. The effect of nonresonant irradiation and of resonant vibrational excitation of the condensed samples is investigated. For thin sample layers metal ions are found, indicating a strong influence of the metal sample holder on the ionization process. In the case of thick sample layers, ions can be produced by special mechanisms far below breakdown.