A photoionization mass spectrometric and threshold photoelectron-photoion coincidence study of vinylbromide (C2H3Br) in the vacuum ultraviolet range of 6-21 eV

The dissociative photoionization of vinyl bromide (C2H3Br) has been investigated by photoionization mass spectrometry (PIMS) and time-of-flight threshold photoelectron-photoion coincidence (TOF-TPEP-ICO) spectrometry using synchrotron radiation. The photoionization efficiency curves of the three most abundant ions, i.e. C2H3Br+, C2H3+ and C2H2+, are measured and analyzed in detail. A C2H3+/Br- photoion-pair formation process has been detected for the first time. Some arguments are provided in favor of the electronic excitation of the C2H3+ fragment and of the isomerization of the C2H2+ ions. The breakdown diagram for these ions in the 9.8-21 eV photon energy range, derived from TOF-TPEPICO mass spectra, is discussed. The involvement of the successive C2H3Br+ ionic states and the role of autoionization of C2H3Br Rydberg states are emphasized. For the two minor HBr+ and Br+ fragment ions only the breakdown diagrams are measured and appearance energies are derived. (C) 2010 Elsevier B.V. All rights reserved.