Photoionization study of CH_3SCH_2Cl formed in the reaction system Cl/Cl_2/CH_3SCH_3

摘要

A photoionization-efficiency spectrum of CH_3SCH_2CI was measured over the wavelength range 108-142 nm by means of a photoionization mass spectrometer coupled to a synchrotron as the source of radiation. Gaseous CH_3SCH_2Cl was generated in a discharge-ftow reactor involving Cl, Cl_2., and CH_3SCH_3 at room temperature via these sequential reactions: Cl+CH_3SCH_3~CH_3SCH_2+HC1; CH_3SCH_2+C1_2~CH_3ScH_2Cl+Cl. According to the PIE spectrum of CH_3SCH_2Cl thus obtained, the ionization energy is (9.077+-0.007) eV. Based on GAUSSIAN-2 calculations, the observed ionization ofCH_3SCH_2Cl near the threshold region is likely to form from singlet CH_3SCH_2Cl ionizing to doublet CH_3SC+-2Cl+; the calculated ionization energy 9.064 eV agrees with the experimental value. The adiabatic ionization energy of CH_3SCH_2 and appearance energy of CH_3SCH; from CH_3SCH_2Cl were determined to be (6.884+-0.008) eV and ( 10.007+- 0.016) eV, respectively; the dissociation energy of the CH_3SCH_2-Cl bond is thus derived to be (72.0+-0.6) kcalmol-l.