Evidence of Site-Specific Fragmentation on Thioacetic Acid, CH3C(O)SH, Irradiated with Synchrotron Radiation around the S 2p and O 1s Regions

ERBEN, M.F.; GERONÉS, M.; ROMANO, R.M.; DELLA VÉDOVA, C.O.

JOURNAL OF PHYSICAL CHEMISTRY A

American Chemical Society

Año: 2006 p. 1 - 9

1089-5639

Site-specific fragmentations following S 2p and O 1s photoexcitation of thioacetic acid, CH3C(O)SH, have been studied by means of synchcrotron radiation. Total ion yield (TIY) spectra were measured and multicoincidence techniques, which include photoelectron-photoion coincidence (PEPICO) and  photoelectronphotoion- photoion coincidence (PEPIPICO) time-of-flight mass spectrometry, were applied. The equivalentcore approximation was employed in order to estimate ionization transition values, and the observed peaks were tentatively assigned. A site-specific fragmentation is moderately observed by comparing the mass spectra collected at resonant energies around the inner and shallow inner shell S 2p and O 1s ionization edges. Beside H+ ion, the most abundant ions observed at the S 2p edge excitation were CH3CO+, SH+, S+, and CH3+. At the O 1s region the large CH3CO+ fragment was depressed, and small CHx + (x = 0, 1, 2, 3), S+, and SH+ fragments were dominant. The dissociation dynamic for the main ion-pair production has been discussed. Two- and three-body dissociation channels have been observed in the PEPIPICO spectra, and the dissociation mechanisms were proposed.