An experimental and theoretical study of ring closing dynamics in HN3

Jianyang Zhang; Peng Zhang; Yuan Chen; Kaijun Yuan; Steven A. Harich; Xiuyan Wang; Zhi Wang; Xueming Yang; Keiji Morokuma; Alec M. Wodtke

doi:10.1039/B600599C

An experimental and theoretical study of ring closing dynamics in HN₃

Jianyang Zhang,^ab Peng Zhang,^c Yuan Chen,^a Kaijun Yuan,^a Steven A. Harich,^a Xiuyan Wang,^ab Zhi Wang,^c Xueming Yang,^a Keiji Morokuma^c and Alec M. Wodtke*^d

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* Corresponding authors

^a State Key Laboratory for Molecular Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Rd. Dalian, Liaoning, P. R. China

^b Department of Physics, Dalian University of Technology, Dalian, China

^c Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia, USA

^d Department of Chemistry and Biochemistry, University of California, Santa Barbara, USA
E-mail: wodtke@chem.ucsb.edu

Abstract

We report on an H(D)-atom Rydberg tagging experiment for H(D)N₃ photolysis providing detailed dynamical information on the wavelength dependence of the H(D) + N₃ channel. We observe subtle yet striking changes in the photochemical dynamics as the photolysis energy passes through ∼5.6 eV. In addition to producing linear azide with an average of ∼40% of available energy appearing as translation, a second H(D)-atom producing channel grows in above this energy releasing only about 15%. An observed (inverse) isotope effect suggests that statistical decomposition on S₀ is unimportant. High level ab initio quantum chemical calculations reveal a transition state to cyclization of the N₃ moiety in H(D)N₃ on the first excited singlet (S₁) surface that is close in energy to the experimentally observed threshold energy for this “slow channel”. Furthermore, the translational energy release of the “slow channel” is energetically consistent with cyclic-N₃ formation. This work provides the clearest presently available insights into how ring closure can occur in azide photochemistry.

Physical Chemistry Chemical Physics

An experimental and theoretical study of ring closing dynamics in HN₃

Abstract

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