Ionization and fragmentation of aromatic and single-bonded hydrocarbons with 50 fs laser pulses at 800 nm

Laser-induced ionization and dissociation of aromatic and single-bonded hydrocarbons, benzene, toluene, cyclopropane, cyclohexane and n-hexane, have been investigated at intensities of 2 x 10(13)-2.5 x 10(14) W cm(-2). Time-of-flight mass spectra, obtained with 800 nm, 50 fs laser pulses, show extensive fragmentation for all molecules above 1 x 10(14) W cm(-2). At 1.3 x 10(13) W cm(-2), the parent ion contribution to the total ionization signal is 30% for benzene, toluene and cyclopropane, and is negligible for cyclohexane and n-hexane. Double-charged parent ions and peak splitting for some of the lighter fragments are observed at high intensity. The correlation between ionization and relative dissociation yields and molecular properties and the participation of field ionization mechanisms are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.