A photoionization mass spectrometric and threshold photoelectron-photoion coincidence study of vinylbromide (C 2H 3Br) in the vacuum ultraviolet range of 6–21 eV

Abstract

The dissociative photoionization of vinyl bromide (C 2H 3Br) has been investigated by photoionization mass spectrometry (PIMS) and time-of-flight threshold photoelectron-photoion coincidence (TOF-TPEPICO) spectrometry using synchrotron radiation. The photoionization efficiency curves of the three most abundant ions, i.e. C 2H 3Br +, C 2 H 3 + and C 2 H 2 + , are measured and analyzed in detail. A C 2 H 3 + / Br - photoion-pair formation process has been detected for the first time. Some arguments are provided in favor of the electronic excitation of the C 2 H 3 + fragment and of the isomerization of the C 2 H 2 + 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 C 2H 3Br + ionic states and the role of autoionization of C 2H 3Br Rydberg states are emphasized. For the two minor HBr + and Br + fragment ions only the breakdown diagrams are measured and appearance energies are derived.