Infrared spectroscopy of gas phase C3H5+:: The allyl and 2-propenyl cations

C3H5+ cations are probed with infrared photodissociation spectroscopy in the 800-3500 cm(-1) region using the method of rare gas tagging. The ions and their complexes with Ar or N-2 are produced in a pulsed electric discharge supersonic expansion cluster source. Two structural isomers are characterized, namely, the allyl (CH2CHCH2+) and 2-propenyl (CH3CCH2+) cations. The infrared spectrum of the allyl cation confirms previous theoretical and condensed phase studies of the C-2v charge delocalized, resonance-stabilized structure. The 2-propenyl cation spectrum is consistent with a C-s symmetry structure having a nearly linear CCC backbone and a hyperconjugatively stabilizing methyl group. (c) 2008 American Institute of Physics.