Infrared Diode Laser Study of Product Energy Distribution in the F + OCS Reaction

摘要

The reaction F + OCS→SF + CO has been investigated by using infrared diode laser spectroscopy to probe both reaction products SF(~2Π_(3/2,1/2)) and CO. Fluorine atoms were prepared by pulsed CO_2 laser photolysis of SF_6 in the presence of OCS. Time-resolved absorption spectra, including many rovibrational lines of SF in the v = 4-3, 3-2, 2-1, and 1-0 bands and those of CO in the v = 2-1 and 1-0 bands, were observed to derive nascent internal energy distributions of the reaction products. The vibrational and rotational energy distributions obtained were Boltzmann-like, and no clear evidence for population inversion was found. Energy partitioning to vibrational modes of SF and CO was only 8 and 0.7% of total available energy (≈ 3500 cm~(-1)), and that to rotational modes of SF and CO was 28% in both cases. These values were not so far from a statistical prior distribution (13, 2.8, 23, and 23%, respectively), indicating that the reaction F + OCS proceeds via an intermediate such as FSCO radical, which may descompose to SF and CO before complete energy randomization. No preference was observed for Λ-doubling components of SF, while spin-orbit component population ~2Π_(1/2)/~2Π_(3/2) was 0.26, which was colder than the prior distribution (~2Π_(1/2)/~2Π_(3/2) = 0.68).