Insights into the dissociative ionization of glycine by PEPICO experiments

Abstract

The fragmentation of glycine (NH₂CH₂COOH) has been studied by photoelectron–photoion coincidence, PEPICO, experiments at 60 eV photon energy. Glycine practically fragments at the ionization threshold, with the charge being on the H₂NCH₂⁺ moiety, due to ejection of an electron from the nitrogen lone pair of the highest occupied molecular orbital. To observe the formation of the complementary cation COOH⁺ further energy is needed. The flexibility with respect to rotation about the C–C, C–N and C–O bonds makes glycine exist in the gas phase in several conformers of both C_s and C₁ point group symmetry in the neutral as well as ion states. The ionization can lead to stabilization of some conformations, rearrangements and, last but not least, H migration between the two moieties. The results of these experiments prove the sensitivity of PEPICO to pin point all these processes.