Laser Desorption electron impact mass spectrometry: Studies of ion radical fragmentation mechanisms and hydrogen/deuterium rearrangement in time‐resolved experiments

Laser desorption of neutral molecules followed by electron impact ionization is shown to produce gaseous ion radicals that undergo fragmentation analogous to that observed with electron impact and field ionization. Spectra were measured of heptanal and four deuterium‐labeled analogs regenerated from bisulfite derivatives, and compared with electron impact, chemical ionization and field ionization spectra published previously. Lifetimes of desorbed neutral molecules and of ions were found to influence the fragmentation process as reflected in isotope patterns. This is explained on the basis of internal energies.