Processes of Laser-Induced Ion Formation in Mass Spectrometry

Mechanisms in molecular SIMS

“…Continuous wave (CW) lasers seem to be a special case because of their low power densities, and perhaps the ionization mechanism with these lasers is strictly thermal evaporation. 236,238 One of the earliest observations of mechanistic significance in LD is the continued emission of neutral species for several microseconds after a laser pulse is terminated.239 This delayed desorption phenomenon has since been shown to apply to ion emission as well.166,240-245 Ejection of sucrose ions was observed to occur for about 300 jus after a 10-ns laser pulse (power density 108 W cm-2).166 Cotter241,242 monitored ion signals from (CH3)4N+CT at intervals up to 500 jus after a 40-ns laser pulse. The intensities of the ions Na4, K+, and ((CH3)4N)+ peaked at times of 5-15 yus after the pulse, and these ions were not detected after 50 jus.…”

Elucidating collision induced dissociation products and reaction mechanisms of protonated uracil by coupling chemical dynamics simulations with tandem mass spectrometry experiments

“…[2][3][4][5][6] Studying the reactivity of biomolecules in the gas phase is a powerful approach, because one can get rid of any effect depending on the environment and thus access directly to important intrinsic properties. In this respect, fast atom bombardment (FAB), [7] matrix assisted laser desorption ionization, [8] electrospray ionization (ESI) [9,10] or desorption electrospray ionization [11,12] techniques are particularly useful and have been extensively used to generate biomolecular ions in the gas phase. In combination with these ionization methods, tandem mass spectrometry through collisional induced dissociation of ions (CID) is also particularly helpful to understand reactivity and to identify characteristic features of biomolecules, because activated ions get enough energy to follow extensive fragmentation.…”