Vibrational IR-Multiphoton Excitation of Thiirane-1-oxide (C_2H_4SO) and d-Thiirane-1-oxide (C_2H_3DSO)

摘要

We report the IR-laser-induced dissociation of C_2H_4SO and of C_2H_3DSO, which was synthesized for the first time. After multiphoton excitation in the frequency range of the SO chromophore (with a large band strength of G = 2.4 pm~2 for C_2H_4SO and 2.8 pm~2 for C_2H_3DSO) in the 1060-1090 cm~(-1) range of the CO_2 laser the product analysis was carried out by static yield measurements using quantitative IR-spectroscopy of ethylene (C_2H_3D, C_2H_4). Effective laser chemical rate constants k_I(st) = (0.70 ± 0.38) cm~2 J~(-1) for C_2H_3DSO with excitation at v(R28) = 1083.48 cm~(-1) and (0.52 ± 0.14) cm~2 J~(-1) for C_2H_4SO were obtained from a fit to the fluence dependence of the photochemical primary yields. A nonlinear intensity dependence of the apparent product yield (P_(app)) was found by using different temporal pulse profiles (singlemode, mode-locked and multimode pulses) at 1083.48 cm~(-1) (9R28) for C_2H_4SO and at 1082.30 cm~(-1) (9R26) for C_2H_3DSO in static yield measurements and time-resolved experiments. FTIR measurements were performed to assign the fundamentals of C_2H_3DSO, which are compared with the harmonic frequencies calculated using GAUSSIAN 92 at MP2 level with different basis sets.