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Title: Quantum-state dependence of product branching ratios in vacuum ultraviolet photodissociation of N{sub 2}

Abstract

The branching ratios for the N({sup 4}S) + N({sup 2}D), N({sup 4}S) + N({sup 2}P), and N({sup 2}D) + N({sup 2}D) channels are measured for the photodissociation of N{sub 2}(X{sup 1}Σ{sub g}{sup +};v{sup ′′}=0,J{sup ′′}) in the vacuum ultraviolet (VUV) region of 100,808–122,159 cm{sup −1} using the VUV–VUV pump-probe approach combined with velocity-map-imaging-photoion detection. No evidence of forming the ground-state N({sup 4}S) + N({sup 4}S) products is found. No potential barrier is observed for the N({sup 2}D) + N({sup 2}D) channel, but the N({sup 4}S) + N({sup 2}P) channel has a small potential barrier of ≈740 cm{sup −1}. The branching ratios are found to depend on the symmetry of predissociative N{sub 2} states instead of the total VUV excitation energy, indicating that N{sub 2} photodissociation is nonstatistical. When the branching ratios for N({sup 4}S) + N({sup 2}D) and N({sup 4}S) + N({sup 2}P) products are plotted as a function of the VUV excitation energy for the valence N{sub 2} {sup 1}Π{sub u} and {sup 1}Σ{sub u}{sup +} states, oscillations in these ratios are observed demonstrating how these channels are competing with each other. These data can be used to select both the velocity and internal states of the atomic products bymore » picking the quantum state that is excited. High-level ab initio potential energy curves of the excited N{sub 2} states are calculated to provide insight into the mechanisms for the observed branching ratios. The calculations predict that the formation of both N({sup 4}S) + N({sup 2}D) and N({sup 4}S) + N({sup 2}P) channels involves potential energy barriers, in agreement with experimental observations. A discussion of the application of the present results to astronomy, planetary sciences, and comets is given.« less

Authors:
; ; ; ;  [1];  [2];
  1. Department of Chemistry, University of California, Davis, CA 95616 (United States)
  2. Laboratoire de Thermodynamique et Modélisation Moléculaire, Faculté de Chimie, USTHB, BP32 El Alia, 16111 Bab Ezzouar, Alger (Algeria)
Publication Date:
OSTI Identifier:
22886984
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 819; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; Journal ID: ISSN 0004-637X
Country of Publication:
United Kingdom
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; BRANCHING RATIO; COMETS; DISSOCIATION; EXCITATION; EXCITED STATES; FAR ULTRAVIOLET RADIATION; FUNCTIONS; GROUND STATES; MOLECULES; PHOTOLYSIS; QUANTUM STATES; SYMMETRY

Citation Formats

Song, Yu, Gao, Hong, Chang, Yih Chung, Jackson, William M., Ng, C. Y., Hammouténe, D, Ndome, H., and Hochlaf, M., E-mail: wmjackson@ucdavis.edu, E-mail: cyng@ucdavis.edu. Quantum-state dependence of product branching ratios in vacuum ultraviolet photodissociation of N{sub 2}. United Kingdom: N. p., 2016. Web. doi:10.3847/0004-637X/819/1/23.
Song, Yu, Gao, Hong, Chang, Yih Chung, Jackson, William M., Ng, C. Y., Hammouténe, D, Ndome, H., & Hochlaf, M., E-mail: wmjackson@ucdavis.edu, E-mail: cyng@ucdavis.edu. Quantum-state dependence of product branching ratios in vacuum ultraviolet photodissociation of N{sub 2}. United Kingdom. https://doi.org/10.3847/0004-637X/819/1/23
Song, Yu, Gao, Hong, Chang, Yih Chung, Jackson, William M., Ng, C. Y., Hammouténe, D, Ndome, H., and Hochlaf, M., E-mail: wmjackson@ucdavis.edu, E-mail: cyng@ucdavis.edu. 2016. "Quantum-state dependence of product branching ratios in vacuum ultraviolet photodissociation of N{sub 2}". United Kingdom. https://doi.org/10.3847/0004-637X/819/1/23.
@article{osti_22886984,
title = {Quantum-state dependence of product branching ratios in vacuum ultraviolet photodissociation of N{sub 2}},
author = {Song, Yu and Gao, Hong and Chang, Yih Chung and Jackson, William M. and Ng, C. Y. and Hammouténe, D and Ndome, H. and Hochlaf, M., E-mail: wmjackson@ucdavis.edu, E-mail: cyng@ucdavis.edu},
abstractNote = {The branching ratios for the N({sup 4}S) + N({sup 2}D), N({sup 4}S) + N({sup 2}P), and N({sup 2}D) + N({sup 2}D) channels are measured for the photodissociation of N{sub 2}(X{sup 1}Σ{sub g}{sup +};v{sup ′′}=0,J{sup ′′}) in the vacuum ultraviolet (VUV) region of 100,808–122,159 cm{sup −1} using the VUV–VUV pump-probe approach combined with velocity-map-imaging-photoion detection. No evidence of forming the ground-state N({sup 4}S) + N({sup 4}S) products is found. No potential barrier is observed for the N({sup 2}D) + N({sup 2}D) channel, but the N({sup 4}S) + N({sup 2}P) channel has a small potential barrier of ≈740 cm{sup −1}. The branching ratios are found to depend on the symmetry of predissociative N{sub 2} states instead of the total VUV excitation energy, indicating that N{sub 2} photodissociation is nonstatistical. When the branching ratios for N({sup 4}S) + N({sup 2}D) and N({sup 4}S) + N({sup 2}P) products are plotted as a function of the VUV excitation energy for the valence N{sub 2} {sup 1}Π{sub u} and {sup 1}Σ{sub u}{sup +} states, oscillations in these ratios are observed demonstrating how these channels are competing with each other. These data can be used to select both the velocity and internal states of the atomic products by picking the quantum state that is excited. High-level ab initio potential energy curves of the excited N{sub 2} states are calculated to provide insight into the mechanisms for the observed branching ratios. The calculations predict that the formation of both N({sup 4}S) + N({sup 2}D) and N({sup 4}S) + N({sup 2}P) channels involves potential energy barriers, in agreement with experimental observations. A discussion of the application of the present results to astronomy, planetary sciences, and comets is given.},
doi = {10.3847/0004-637X/819/1/23},
url = {https://www.osti.gov/biblio/22886984}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 819,
place = {United Kingdom},
year = {2016},
month = {3}
}