Distinct collision processes in mass spectrometry: Charge inversion reactions and peptide ion soft -landing

Collisions can be classified into three categories: (i) elastic—collisions in which the total kinetic energy, momentum, and internal energy of the colliding partners are each conserved; (ii) reactive—collisions in which there is a change in chemical composition; and (iii) inelastic—collisions in which there is a change in internal energy. In this thesis distinct cases of each kind of collision—elastic, reactive, and inelastic—performed in mass spectrometers are the subject of investigation. Elastic collisions were explored by intact deposition of peptide ions onto surfaces. Elastic collisions are thought to be responsible for the removal of translational energy that allows intact ion deposition or ion soft-landing. The fundamentals of ion soft-landing for the case of peptide ions were investigated in detail. This study was triggered by ongoing efforts in our laboratory to develop a method to obtain arrays of proteins by ion soft-landing using mass spectrometric techniques. Reactive collisions in mass spectrometry provide invaluable information on the nature of reactions that proceed by ionic intermediates, including mechanisms of reaction, thermochemistry and ion dynamics. In the case of collisions with solid targets, ion/surface reactions represent possible methods for chemically modifying surfaces, as well as possible methods for surface analysis. A special kind of reactive scattering process namely charge inversion reactions were investigated in the case of nitrobenzene upon collisions with organic monolayers. Collisions of ions with surfaces leading to charge inversion was presented as an alternative to conventional collisional activation to increase the internal energy of a system to effect its dissociation. Finally, inelastic collisions were investigated for the structural analysis and for the elucidation of energy transfer mechanisms of cation-bound dimers upon collisions with gaseous and solid targets, respectively