Photodissociation spectroscopy and dynamics of the methylthio radical (CH3S)

Abstract

The photodissociation spectroscopy and dynamics of the CH 3 S and CD 3 S radicals have been investigated using fast radical beam photofragment spectroscopy of the à 2 A 1 ←X 2 E electronic band (T 0 Х26 400 cm Ϫ1) and an unstructured band near 45 600 cm Ϫ1. At all energies, only one major channel, CH 3 (X 2 A 2 Љ)ϩS(3 P j), was observed. Photofragment yield spectra for the à 2 A 1 ←X 2 E electronic band show resolved vibrational progressions extending well beyond those seen in laser-induced fluorescence studies of this band. Photofragment translational energy distributions yield the S(3 P j) fine-structure distribution for each vibrational level of the CH 3 product. Photofragment angular distributions were found to be highly anisotropic ͑␤ϭϪ0.2 to Ϫ1.0Ϯ0.1͒ with increasing anisotropy at higher photon energies. The results yield a refined heat of formation for CH 3 S ͑1.346Ϯ0.018 eV͒ as well as the mechanism by which the à 2 A 1 state is predissociated. Results at 45 600 cm Ϫ1 imply that dissociation occurs on the repulsive B 2 A 2 state.

Imaging CH3SH photodissociation at 204 nm: the SH + CH3 channel

“…The 3p z probe photon energy is above the threshold of the CH 3 S + hv -CH 3 + S( 3 P j ) predissociation process. [33][34][35] In our experiments, the CH 3 S species thus formed can be further dissociated by a probe photon as shown in Fig. 1A.…”

Velocity Map Imaging Study of the Photodissociation of CH3SH: Internal Energy Distribution of the SH Fragment

“…The methylthio radical (CH 3 S) is known to have the ffi 2 A 1 state within this energetic range. [20] This state is bound, but known to predissociate via the crossing of three repulsive surfaces that produce methyl and sulphur in their electronic ground states. The faster more intense feature between 1.2 and 2 eV kinetic energy shows a series of peaks which are partially resolved, indicative of internal excitation in some fragment vibrational mode, since they all seem to be similarly spaced with a difference in energy of around 1400 cm…”

Novel gaseous transient species: Generation and characterization

“…; many experimental and theoretical calculations have been performed to investigate its geometric and electronic structures [58,59] . Enlightened by our molecular sieve catalysis decomposition of RONO (R = alkyl) for generating alkoxy radicals, we carried out first the thermolysis of the dimethyl disulfide (CH 3 SSCH 3 ), and the weakest S-S bond was broken at 285(± 0.5)℃, with the catalysis of 5 Å molecular sieve.…”