Unraveling the Rich Fragmentation Dynamics Associated with S-H Bond Fission Following Photoexcitation of H 2S at Wavelengths ∼129.1 nm

Z.J. Luo, Y.C. Wu, S.K. Yang, Z.X. Li, W. Hua, Z.C. Chen, L. Che, X.G. Wang, Michael N R Ashfold*, K.J. Yuan*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

H2S is being detected in the atmospheres of ever more interstellar bodies, and photolysis is an important mechanism by which it is processed. Here, we report H Rydberg atom time-of-flight measurements following the excitation of H2S molecules to selected rotational (JKaKc′) levels of the 1B1 Rydberg state associated with the strong absorption feature at wavelengths of λ ∼ 129.1 nm. Analysis of the total kinetic energy release spectra derived from these data reveals that all levels predissociate to yield H atoms in conjunction with both SH(A) and SH(X) partners and that the primary SH(A)/SH(X) product branching ratio increases steeply with ⟨Jb2⟩, the square of the rotational angular momentum about the b-inertial axis in the excited state. These products arise via competing homogeneous (vibronic) and heterogeneous (Coriolis-induced) predissociation pathways that involve coupling to dissociative potential energy surfaces (PES(s)) of, respectively, 1A″ and 1A′ symmetries. The present data also show H + SH(A) product formation when exciting the JKaKc′ = 000 and 111 levels, for which ⟨Jb2⟩ = 0 and Coriolis coupling to the 1A′ PES(s) is symmetry forbidden, implying the operation of another, hitherto unrecognized, route to forming H + SH(A) products following excitation of H2S at energies above ∼9 eV. These data can be expected to stimulate future ab initio molecular dynamic studies that test, refine, and define the currently inferred predissociation pathways available to photoexcited H2S molecules.
Original languageEnglish
Pages (from-to)3351-3360
Number of pages10
JournalJournal of Physical Chemistry A
Volume128
Issue number17
Early online date23 Apr 2024
DOIs
Publication statusPublished - 2 May 2024

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© 2024 American Chemical Society.

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