Vacuum ultraviolet photodissociation of sulfur dioxide and its implications for oxygen production in the early Earth's atmosphere

Yao Chang; Yanlin Fu; Zhichao Chen; Zijie Luo; Yarui Zhao; Zhenxing Li; Weiqing Zhang; Guorong Wu; Bina Fu; Dong H Zhang; Michael N R Ashfold; Xueming Yang; Kaijun Yuan

doi:10.1039/d3sc03328g

Vacuum ultraviolet photodissociation of sulfur dioxide and its implications for oxygen production in the early Earth's atmosphere

Chem Sci. 2023 Aug 1;14(31):8255-8261. doi: 10.1039/d3sc03328g. eCollection 2023 Aug 9.

Authors

Yao Chang¹, Yanlin Fu¹, Zhichao Chen¹, Zijie Luo^{1

2}, Yarui Zhao¹, Zhenxing Li¹, Weiqing Zhang¹, Guorong Wu¹, Bina Fu^{1

3

4}, Dong H Zhang^{1

4

5}, Michael N R Ashfold⁶, Xueming Yang^{1

4

5}, Kaijun Yuan^{1

3

4}

Affiliations

¹ State Key Laboratory of Molecular Reaction Dynamics, Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China kjyuan@dicp.ac.cn bina@dicp.ac.cn xmyang@dicp.ac.cn.
² Marine Engineering College, Dalian Maritime University Liaoning 116026 China.
³ University of Chinese Academy of Sciences Beijing 100049 P. R. China.
⁴ Hefei National Laboratory Hefei 230088 China.
⁵ Department of Chemistry, Center for Advanced Light Source Research, College of Science, Southern University of Science and Technology Shenzhen 518055 China.
⁶ School of Chemistry, University of Bristol Bristol BS8 1TS UK.

Abstract

The emergence of molecular oxygen (O₂) in the Earth's primitive atmosphere is an issue of major interest. Although the biological processes leading to its accumulation in the Earth's atmosphere are well understood, its abiotic source is still not fully established. Here, we report a new direct dissociation channel yielding S(¹D) + O₂(a¹Δ_g/X³Σ_g^-) products from vacuum ultraviolet (VUV) photodissociation of SO₂ in the wavelength range between 120 and 160 nm. Experimental results show O₂ production to be an important channel from SO₂ VUV photodissociation, with a branching ratio of 30 ± 5% at the H Lyman-α wavelength (121.6 nm). The relatively large amounts of SO₂ emitted from volcanic eruptions in the Earth's late Archaean eon imply that VUV photodissociation of SO₂ could have provided a crucial additional source term in the O₂ budget in the Earth's primitive atmosphere. The results could also have implications for abiotic oxygen formation on other planets with atmospheres rich in volcanically outgassed SO₂.