Dissociative ionization of halogenated ethylenes in intense femtosecond laser pulses

The interaction of chloro-ethylene (H2CCHCl), bromo-ethylene (H2CCHBr), and 2-chloro-ethenylsilane (H3SiCHCHCl) with 50 fs linearly polarized laser pulses of 800 and 400 nm at intensities up to 2×1014 and 7×1012 W cm−2, respectively, has been studied using a time-of-flight mass spectrometer. At 400 nm extensive fragmentation is observed, while at 800 nm the presence of singly and doubly charged parent ions and of multiply charged atomic ions in the mass spectra attests to a reduction of fragmentation in favour of multiple ionization of the parent followed by Coulomb explosion. The silane compound dissociates more easily, its multicharged atomic fragments appear at lower intensities and are ejected with higher kinetic energies than the chlorine and bromine derivatives. The results reveal that laser–molecule coupling is influenced by the molecular properties and that energy channeling increases with molecular size.