Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion

doi:https://doi.org/10.1063/1.4922931

Title: Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion

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Abstract

The acetylenic CH stretch mode (ν{sub 1}) of propargyl (H{sub 2}CCCH) radical has been studied at sub-Doppler resolution (∼60 MHz) via infrared laser absorption spectroscopy in a supersonic slit-jet discharge expansion, where low rotational temperatures (T{sub rot} = 13.5(4) K) and lack of spectral congestion permit improved determination of band origin and rotational constants for the excited state. For the lowest J states primarily populated in the slit jet cooled expansion, fine structure due to the unpaired electron spin is resolved completely, which permits accurate analysis of electron spin-rotation interactions in the vibrationally excited states (ε{sub aa} = − 518.1(1.8), ε{sub bb} = − 13.0(3), ε{sub cc} = − 1.8(3) MHz). In addition, hyperfine broadening in substantial excess of the sub-Doppler experimental linewidths is observed due to nuclear spin–electron spin contributions at the methylenic (—CH{sub 2}) and acetylenic (—CH) positions, which permits detailed modeling of the fine/hyperfine structure line contours. The results are consistent with a delocalized radical spin density extending over both methylenic and acetylenic C atoms, in excellent agreement with simple resonance structures as well as ab initio theoretical calculations.

Authors:

Chang, Chih-Hsuan; Nesbitt, David J. ^[1]

JILA, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309, USA and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309 (United States)

Publication Date:: 2015-06-28

OSTI Identifier:: 22489545

Resource Type:: Journal Article

Journal Name:: Journal of Chemical Physics

Additional Journal Information:: Journal Volume: 142; Journal Issue: 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; DENSITY; ELECTRONS; EXCITED STATES; FINE STRUCTURE; HYPERFINE STRUCTURE; INFRARED SPECTRA; INTERACTIONS; MHZ RANGE; PROPARGYL RADICALS; SIMULATION; SPIN

Citation Formats


                    Chang, Chih-Hsuan, and Nesbitt, David J. Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion.  United States: N. p., 2015. 
        Web.  doi:10.1063/1.4922931.

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                    Chang, Chih-Hsuan, & Nesbitt, David J. Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion.  United States.  https://doi.org/10.1063/1.4922931

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                    Chang, Chih-Hsuan, and Nesbitt, David J. Sun .  
        "Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion".  United States.  https://doi.org/10.1063/1.4922931.

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@article{osti_22489545,

  title        = {Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion},

  author       = {Chang, Chih-Hsuan and Nesbitt, David J.},

  abstractNote = {The acetylenic CH stretch mode (ν{sub 1}) of propargyl (H{sub 2}CCCH) radical has been studied at sub-Doppler resolution (∼60 MHz) via infrared laser absorption spectroscopy in a supersonic slit-jet discharge expansion, where low rotational temperatures (T{sub rot} = 13.5(4) K) and lack of spectral congestion permit improved determination of band origin and rotational constants for the excited state. For the lowest J states primarily populated in the slit jet cooled expansion, fine structure due to the unpaired electron spin is resolved completely, which permits accurate analysis of electron spin-rotation interactions in the vibrationally excited states (ε{sub aa} = − 518.1(1.8), ε{sub bb} = − 13.0(3), ε{sub cc} = − 1.8(3) MHz). In addition, hyperfine broadening in substantial excess of the sub-Doppler experimental linewidths is observed due to nuclear spin–electron spin contributions at the methylenic (—CH{sub 2}) and acetylenic (—CH) positions, which permits detailed modeling of the fine/hyperfine structure line contours. The results are consistent with a delocalized radical spin density extending over both methylenic and acetylenic C atoms, in excellent agreement with simple resonance structures as well as ab initio theoretical calculations.},

  doi          = {10.1063/1.4922931},

  url          = {https://www.osti.gov/biblio/22489545},
  journal      = {Journal of Chemical Physics},

  issn         = {0021-9606},

  number       = 24,

  volume       = 142,

  place        = {United States},

  year         = {2015},

  month        = {6}

}

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