Third harmonic generation in xenon was used to produce vacuum ultraviolet light at a fixed wavelength of 118 nm. These photons were able to ionize a number of organic molecules with negligible yields of fragmentation ions. This method yielded far simpler mass spectra than those utilizing electron impact ionization. Absolute photoionization cross sections were measured for six organic compounds at 118.2 nm.
J. H. Arps, C. H. Chen, M. P. McCann, and I. Datskou, "Ionization of Organic Molecules Using Coherent Vacuum Ultraviolet Light," Appl. Spectrosc. 43, 1211-1214 (1989)