Enhanced reactivity of fluorine with para-hydrogen in cold interstellar clouds by resonance-induced quantum tunnelling

Tiangang Yang; Long Huang; Chunlei Xiao; Jun Chen; Tao Wang; Dongxu Dai; Francois Lique; Millard H Alexander; Zhigang Sun; Dong H Zhang; Xueming Yang; Daniel M Neumark

doi:10.1038/s41557-019-0280-3

Enhanced reactivity of fluorine with para-hydrogen in cold interstellar clouds by resonance-induced quantum tunnelling

Nat Chem. 2019 Aug;11(8):744-749. doi: 10.1038/s41557-019-0280-3. Epub 2019 Jun 24.

Authors

Tiangang Yang¹, Long Huang^{1

2}, Chunlei Xiao¹, Jun Chen¹, Tao Wang³, Dongxu Dai¹, Francois Lique⁴, Millard H Alexander⁵, Zhigang Sun⁶, Dong H Zhang¹, Xueming Yang^{7

8}, Daniel M Neumark^{9

10}

Affiliations

¹ State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China.
² University of Chinese Academy of Sciences, Beijing, China.
³ Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen, China.
⁴ Laboratoire Ondes et Milieux Complexes, CNRS-Université Le Havre Normandie and Institut Universitaire de France, Le Havre, France.
⁵ Department of Chemistry and Biochemistry and Institute for Physical Sciences and Technology, University of Maryland, College Park, MD, USA. mha@umd.edu.
⁶ State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China. zsun@dicp.ac.cn.
⁷ State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China. xmyang@dicp.ac.cn.
⁸ Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen, China. xmyang@dicp.ac.cn.
⁹ Department of Chemistry, University of California at Berkeley, Berkeley, CA, USA. dneumark@berkeley.edu.
¹⁰ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. dneumark@berkeley.edu.

PMID: 31235895
DOI: 10.1038/s41557-019-0280-3

Abstract

Chemical reactions are important in the evolution of low-temperature interstellar clouds, where the quantum tunnelling effect becomes significant. The F + para-H₂ → HF + H reaction, which has a significant barrier of 1.8 kcal mol^-1, is an important source of HF in interstellar clouds; however, the dynamics of this quantum-tunnelling-induced reactivity at low temperature is unknown. Here, we show that this quantum tunnelling is caused by a post-barrier resonance state. Quantum-state-resolved crossed-beam scattering measurements reveal that this resonance state has a collision energy of ~5 meV and a lifetime of ~80 fs, which are in excellent agreement with a recent anion photoelectron spectroscopic study. Accurate quantum reactive scattering calculations on the new iCSZ-LWAL potential energy surfaces provides a detailed explanation of the experimental results. The reaction rate for this system was also theoretically determined accurately at temperatures as low as 1 K.