Influence of stimulated desorption on molecular fragmentation

Caroline R. Ayre; Lorenza Moro; Christopher H. Becker

doi:10.1117/12.180857

21 July 1994 Influence of stimulated desorption on molecular fragmentation

Caroline R. Ayre, Lorenza Moro, Christopher H. Becker

Proceedings Volume 2125, Laser Techniques for Surface Science; (1994) https://doi.org/10.1117/12.180857
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

Abstract

The mass spectral fragmentation of l-tryptophan has been investigated as a function of desorption technique and photoionization method using 7 keV Ar⁺ static sputtering, 355 nm pulsed laser-induced desorption, and thermal desorption at 150 to 200 degree(s)C in conjunction with 118 nm (10.49 eV), 266 nm (4.66 eV), and 355 nm (3.50 eV) laser positionization. In addition, ion-stimulated desorption of neutrals has been compared with positive secondary ion data. Molecular fragmentation is dominated by the internal energy contribution of the desorption process rather than photoionization method; fragmentation is maximal with ion-stimulated desorption and minimal with thermal desorption. Furthermore, single-photon ionization with 118 nm generally results in less fragmentation than multiphoton ionization (MPI). Finally, the effect of laser pulse width on the 266 nm MPI of thermally-desorbed neutral species has been explored. The use of 35 ps rather than 5 ns laser pulses at 266 nm has been explored. The use of 35 ps rather than 5 ns laser pulses at 266 nm has been found to cause a decrease in the molecular fragmentation of l-tryptophan. These results have implications for the surface analysis of labile organic compounds.

Citation Download Citation

Caroline R. Ayre, Lorenza Moro, and Christopher H. Becker "Influence of stimulated desorption on molecular fragmentation", Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); https://doi.org/10.1117/12.180857

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