A. Danon, E. Kolodney, A. Amirav
1988
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0
Influential Citations
38
Citations
Journal
Surface Science
Abstract
Abstract The dissociation of 1-iodopropane due to scattering from single crystal diamond (111) was studied at hyperthermal kinetic energies (1–10 eV). 1-Iodopropane was accelerated in a hydrogen seeded supersonic molecular beam. Dissociation probabilities up to 4% at a kinetic energy of 8 eV were measured using a quadrupole mass spectrometer (QMS). The dissociation was mostly into iodine atoms and not through the lower energy channel, namely the elimination reaction into propylene and hydrogen iodide. The angular distribution of the scattered iodine atoms was shifted from the specular angle into the grazing direction (supraspecular scattering). This shift and angular difference from the scattered molecular angular distribution, as well as the fragment identity, preclude statistical dissociation after vibrational excitation and energy redistribution. We have also found dissociative ionization resulting in the generation of positive propyl and negative iodine ions. The kinetic energy dependence of both the natural iodine atoms and positive propyl ions could be fitted to the same type of empirical formula resulting in an identical threshold of 3.7 eV. This effective threshold which is much higher than that of the elimination (0.84 eV), or the direct dissociation (2.3 eV), suggests that the dissociation occurs after collision induced electronic excitation and predissociation, or ionization and subsequent neutralization. The kinetic energy of the scattered undissociated molecules, as well as that of the generated atomic iodine, was measured using a time-of-flight technique. This information, combined with internal vibrational temperature measurement of the scattered molecules, resulted in the determination of relative energy transferred to the surface and to the vibrational-rotational degrees of freedom.