Photodissociation of S2 (X3ςg -, a1Δg, and b1ςg +) in the 320-205 nm Region

Z. F. Sun, Z. Farooq, D. H. Parker, P. J. J. Martin, C. M. Western

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Abstract

Photodissociation of vibrationally and electronically excited sulfur dimer molecules (S2) has been studied in a combined experimental and computational quantum chemistry study in order to characterize bound-continuum transitions. Ab initio quantum chemistry calculations are carried out to predict the potential energy curves, spin-orbit coupling, transition moments, and bound-continuum spectra of S2 for comparison with the experimental data. The experiment uses velocity map imaging to measure S-atom production following S2 photoexcitation in the ultraviolet region (320-205 nm). A pulsed electric discharge in H2S produces ground-state S2 X3ςg -(v = 0-15) as well as electronically excited singlet sulfur and b1ςg +(v = 0, 1), and evidence is presented for the production and photodissociation of S2 a1Δg. In a previous paper, we reported threshold photodissociation of S2X3ςg -(v = 0) in the 282-266 nm region. In the present study, S(3PJ) fine structure branching and angular distributions for photodissociation of S2 (X3ςg -(v = 0), a1Δg and b1ςg +) via the B″3IIu, B3ςu - and 11IIu excited states are reported. In addition, photodissociation of the X3ςg -(v = 0) state of S2 to the second dissociation limit producing S(3P2) + S(1D) is characterized. The present results on S2 photodynamics are compared to those of the well-studied electronically isovalent O2 molecule.

Original languageEnglish
Pages (from-to)6886-6896
Number of pages11
JournalJournal of Physical Chemistry A
Volume123
Issue number32
Early online date19 Jul 2019
DOIs
Publication statusPublished - 15 Aug 2019

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