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Gas‐phase Ionization of Polyatomic Molecules via Interactions with Positrons
Author(s) -
McLuckey Scott A.,
Hulett Lester D.,
Xu Jun,
Lewis T. A.
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(199602)10:3<269::aid-rcm463>3.0.co;2-r
Subject(s) - chemistry , polyatomic ion , gas phase , ionization , molecule , phase (matter) , chemical physics , atomic physics , ion , organic chemistry , physics
Positrons, electron anti‐particles, can ionize isolated gaseous molecules by a variety of mechanisms. The dominant mechanism is determined primarily by positron kinetic energy. Fast positrons appear to ionize in direct analogy with ionization by fast electrons. At positron energies below the ionization energy of the molecule, ionization can take place in conjunction with the formation of positronium, the bound electron‐positron species. The resulting mass spectra can be interpreted on the basis of a two‐step mechanism involving electron transfer to the positron followed by unimolecular decomposition of the molecular ion. At kinetic energies below the threshold for postironium formation, ionization can proceed via an apparent positron capture process. This mechanism is far more selective than the mechanisms operative at higher kinetic energies and can result in much more extensive fragmentation than is observed with either impact ionization or positronium formation.