Decomposing the First Absorption Band of OCS Using Photofragment Excitation Spectroscopy

作者：Toulson Benjamin W; Murray Craig^*

来源：Journal of Physical Chemistry A, 2016, 120(34): 6745-6752.

DOI：10.1021/acs.jpca.6b06060

Photofragment excitation spectra of Carbonyl sulfide (OCS) have been recorded from 212-260 nm by state-selectively probing either electronically excited S(D-1) or ground state S(P-3) photolysis products via 2 + 1 resonance-enhanced multiphoton ionization. Probing the major S(D-1) product results in a broad, unstructured action spectrum that reproduces the overall shape of the first absorption band. In contrast, spectra obtained probing S(P-3) products display prominent resonances superimposed on a broad continuum; the resonances correspond to the diffuse vibrational structure observed in the conventional absorption spectrum. The vibrational structure is assigned to four progressions, each dominated by the C-S stretch, v(1), following direct excitation to quasi-bound singlet and triplet states. The S(P-3(J)) products are formed with a near-statistical population distribution over the J = 2, 1, and 0 spin orbit levels across the wavelength range investigated. Although a minor contributor to the S atom yield near the peak of the absorption cross section, the relative yield of S(P-3) increases significantly at longer wavelengths. The experimental measurements validate recent theoretical work characterizing the electronic states responsible for the first absorption band by Schmidt and co-workers.

• 出版日期2016-9-1