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Title: Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm –1

Abstract

Photodissociation of CO is a fundamental chemical mechanism for mass-independent oxygen isotope fractionation in the early Solar System. Branching ratios of photodissociation channels for individual bands quantitatively yield the trapping efficiencies of atomic oxygen resulting into oxides. We measured the branching ratios for the spin-forbidden and spin-allowed photodissociation channels of 12C16O in the vacuum ultraviolet (VUV) photon energy region from 106 250 to 107 800 cm–1 using the VUV laser time-slice velocity-map imaging photoion technique. The excitations to four 1Π bands and three 1Σ+ bands of 12C16O were identified and investigated. The branching ratios for the product channels C(3P) + O(3P), C(1D) + O(3P), and C(3P) + O(1D) of these predissociative states strongly depend on the electronic and vibrational states of CO being excited. Furthermore, by plotting the branching ratio of the spin-forbidden dissociation channels versus the excitation energy from 102 500 to 110 500 cm–1 that has been measured so far, the global pattern of the 1Π–3Π interaction that plays a key role in the predissociation of CO is revealed and discussed.

Authors:
 [1];  [2];  [3];  [3]; ORCiD logo [4]; ORCiD logo [3]; ORCiD logo [3]
  1. Univ. of California, Davis, CA (United States); Univ. of California, San Francisco, CA (United States)
  2. Univ. of California, Davis, CA (United States); Chinese Academy of Sciences (CAS), Beijing (China)
  3. Univ. of California, Davis, CA (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1477706
Report Number(s):
LA-UR-18-28856
Journal ID: ISSN 1089-5639
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 122; Journal Issue: 41; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Planetary Sciences

Citation Formats

Shi, Xiaoyu, Gao, Hong, Yin, Qing -Zhu, Chang, Yih -Chung, Wiens, Roger Craig, Jackson, William M., and Ng, Cheuk -Yiu. Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm –1. United States: N. p., 2018. Web. https://doi.org/10.1021/acs.jpca.8b08058.
Shi, Xiaoyu, Gao, Hong, Yin, Qing -Zhu, Chang, Yih -Chung, Wiens, Roger Craig, Jackson, William M., & Ng, Cheuk -Yiu. Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm –1. United States. https://doi.org/10.1021/acs.jpca.8b08058
Shi, Xiaoyu, Gao, Hong, Yin, Qing -Zhu, Chang, Yih -Chung, Wiens, Roger Craig, Jackson, William M., and Ng, Cheuk -Yiu. Thu . "Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm –1". United States. https://doi.org/10.1021/acs.jpca.8b08058. https://www.osti.gov/servlets/purl/1477706.
@article{osti_1477706,
title = {Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm –1},
author = {Shi, Xiaoyu and Gao, Hong and Yin, Qing -Zhu and Chang, Yih -Chung and Wiens, Roger Craig and Jackson, William M. and Ng, Cheuk -Yiu},
abstractNote = {Photodissociation of CO is a fundamental chemical mechanism for mass-independent oxygen isotope fractionation in the early Solar System. Branching ratios of photodissociation channels for individual bands quantitatively yield the trapping efficiencies of atomic oxygen resulting into oxides. We measured the branching ratios for the spin-forbidden and spin-allowed photodissociation channels of 12C16O in the vacuum ultraviolet (VUV) photon energy region from 106 250 to 107 800 cm–1 using the VUV laser time-slice velocity-map imaging photoion technique. The excitations to four 1Π bands and three 1Σ+ bands of 12C16O were identified and investigated. The branching ratios for the product channels C(3P) + O(3P), C(1D) + O(3P), and C(3P) + O(1D) of these predissociative states strongly depend on the electronic and vibrational states of CO being excited. Furthermore, by plotting the branching ratio of the spin-forbidden dissociation channels versus the excitation energy from 102 500 to 110 500 cm–1 that has been measured so far, the global pattern of the 1Π–3Π interaction that plays a key role in the predissociation of CO is revealed and discussed.},
doi = {10.1021/acs.jpca.8b08058},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 41,
volume = 122,
place = {United States},
year = {2018},
month = {9}
}

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Figures / Tables:

Figure 1 Figure 1: Carbon ion PHOFEX spectra for the four 1$\Pi$ bands of 12C16O: (a) band #13 with upper state 1$\Pi$ (v′ = 2), (b) band #14 with upper state 1$\Pi$ (v′ = 2), (c) band #15A with upper state 1$\Pi$(v′ = 0), and (d) band #15B with upper state (5p$π$)more » 1$\Pi$ (v′ = 0). The relative intensities of these bands were not normalized to the corresponding VUV laser intensities.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.