Kinetic energy release distribution in the fragmentation of energy-selected iodopropane ions

Abstract

Abstract The technique of threshold photoelectron-photoion coincidence (PEPICO) has been employed to determine the average kinetic energy release and the kinetic energy release distribution (KERD) for the iodine loss from 1- and 2-iodopropane ions as a function of the ion internal energy. The KERDs at all precursor-ion energies investigated (0–3 eV excess energy) have the shape of statistically expected distributions, 1-iodopropane ions which dissociate with an apparent 0.16 eV reverse activation barrier, are shown to isomerize at low energies prior to dissociation, to produce subsequently the 2-propyl C 3 H 7 − structure. At high energies they may form a different C 3 H 7 − isomer. The experimentally observed average kinetic energy releases are approximately a factor of 2 greater than expected statistically suggesting that not all vibrational modes participate in the energy disposal. The secondary dissociation of the C 3 H 7 − isomers to C 3 H 3 which is inhibited by a reverse activation barrier of = 0.4 eV indicates that the 1- and 2-iodopropane ions dissociate 75% and 60% respectively, to form the excited 1( 2 P 1/2 ) atoms.