Occurs when a sample is irradiated with a laser beam. In the irradiation of gaseous samples, ionization occurs
via a single- or multi-photon process. In the case of solid samples, ionization occurs
via a thermal process.
Sources:
Orange Book, 2nd ed., p. 204 (https://media.iupac.org/publications/analytical_compendium/)
PAC, 1991, 63, 1541. 'Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)' on page 1548 (https://doi.org/10.1351/pac199163101541)