Photodissociation of H<sub>2</sub>S: A New Pathway for the Production of Vibrationally Excited Molecular Hydrogen in the Interstellar Medium
Yarui Zhao, Junjie Chen, Zijie Luo, Zhenxing Li, Shuaikang Yang, Yao Chang, Feng An, Zhichao Chen, Jiayue Yang, Guorong Wu, Weiqing Zhang, Xixi Hu, Daiqian Xie, Hongbin Ding, Kaijun Yuan, Xueming Yang
Abstract
Hydrogen sulfide (H 2 S) is the most abundant S-bearing molecule in the solar nebula. Although its photochemistry has been studied for decades, the H 2 fragment channel is still not well-understood. Herein, we describe the photodissociation dynamics of H 2 S + h v → S( 1 S) + H 2 (X 1 Σ g + ) with the excitation wavelength of 122 nm ≤ λ ≤ 136 nm. The results reveal that the H 2 (X) fragments formed are significantly vibrationally excited, with the quantum yields of ∼87% of H 2 (X) fragments populated in vibrational levels v ″ = 3, 4, 5, and 6. Theoretical analysis suggest that these H 2 products are formed on the H 2 S 4 1 A ′ state surface following a nonadiabatic transition via an avoided crossing from the 3 1 A ′ to 4 1 A ′ state. The estimated quantum yield of the S( 1 S) + H 2 channel is ∼0.05, implying this channel should be incorporated into the appropriate interstellar chemistry models.