Photofragment translational spectroscopy of 1,2-butadiene at 193 nm

Photofragment translational spectroscopy has been used to investigate the d issociation dynamics of 1,2-butadiene at 193 nm. Ionization of scattered ph otoproducts was accomplished using tunable VUV synchrotron radiation at the Advanced Light Source. Two product channels are observed: CH3+C3H3 and C4H 5+H. The C3H3 product can be identified as the propargyl radical through me asurement of its photoionization efficiency curve, whereas the C4H5 product cannot be identified definitively. The translational energy P(E-T) distrib utions suggest that both channels result from internal conversion to the gr ound electronic state followed by dissociation. The P(E-T) distribution for the C4H5 product is sharply truncated below 7 kcal/mol, indicating spontan eous decomposition of the slowest C4H5 product. (C) 2001 American Institute of Physics.