Photodissociation of H₂S: A New Pathway for the Production of Vibrationally Excited Molecular Hydrogen in the Interstellar Medium

This is the authors' abstract. We don't add key points for this paper.

Hydrogen sulfide (H2S) is the most abundant S-bearing molecule in the solar nebula. Although its photochemistry has been studied for decades, the H2 fragment channel is still not well-understood. Herein, we describe the photodissociation dynamics of H2S + hv → S(1S) + H2(X1Σg+) with the excitation wavelength of 122 nm ≤ λ ≤ 136 nm. The results reveal that the H2(X) fragments formed are significantly vibrationally excited, with the quantum yields of ∼87% of H2(X) fragments populated in vibrational levels v″ = 3, 4, 5, and 6. Theoretical analysis suggest that these H2 products are formed on the H2S 41A′ state surface following a nonadiabatic transition via an avoided crossing from the 31A′ to 41A′ state. The estimated quantum yield of the S(1S) + H2 channel is ∼0.05, implying this channel should be incorporated into the appropriate interstellar chemistry models.