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Molecular photofragmentation during non‐resonant multiphoton ionization of sputtered species
Author(s) -
Coon S. R.,
Calaway W. F.,
Pellin M. J.,
Burnett J. W.,
White J. M.
Publication year - 1993
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740201212
Subject(s) - photoionization , ionization , atomic physics , chemistry , ion , fragmentation (computing) , physics , organic chemistry , computer science , operating system
To assess the quantitative analytical capabilities of laser post‐ionization of sputtered neutrals, the photoionization of sputtered Cu, Al and Ru atoms and clusters was investigated. By measuring velocity distributions using both resonant and non‐resonant photoionization of the atoms and one‐photon and two‐photon ionization of the clusters, photogragmentation of clusters was found to be significant. Atomic velocity distributions measured using non‐resonant ionization peaked at the same velocity as the respective dimer distribution, indicating that the majority of the non‐resonant atomic ion signal is from photogragmented dimers. The contribution to the dimer ion signal from photogragmentation of the trimer varied with the two‐photon laser power density. Domination of the atomic photoion channel by molecule fragmentation appears to be a general phenomenon that must be accounted for in all gas‐phase multiphoton non‐resonant ionization experiments at easily achievable laser power densities (≤ 10 8 W cm −2 ). To minize photogragmentation effects, atoms should be ionized resonantly and clusters should be onephoton ionized.