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Experiments and Calculations on Photoionization and Dissociative Photoionization of CH 2 CO
Author(s) -
Chiang SuYu,
Fang YungSheng,
Bahou Mohammed,
Sankaran K.
Publication year - 2004
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200400103
Subject(s) - photoionization , chemistry , dissociation (chemistry) , ion , ionization , mass spectrometry , atomic physics , photoionization mode , physics , organic chemistry , chromatography
The dissociative photoionization of molecular‐beam cooled CH 2 CO in a region of ˜10–20 eV was investigated with photoionization mass spectrometry using a synchrotron radiation as the light source. Photoionization efficiency curves of CH 2 CO + and of observed fragment ions CH 2 + , CHCO + , HCO + , C 2 O + , CO + , and C 2 H 2 + were measured to determine their appearance energies. Relative branching ratios as a function of photon energy were determined. Energies for formation of these observed fragment ions and their neutral counterparts upon ionization of CH 2 CO are computed with the Gaussian‐3 method. Dissociative photoionization channels associated with six observed fragment ions are proposed based on comparison of determined appearance energies and predicted energies. The principal dissociative processes are direct breaking of C=C and C‐H bonds to form CH 2 + + CO and CHCO + + H, respectively; at greater energies, dissociation involving H migration takes place.