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Title: Sub-Doppler infrared spectroscopy of CH 2OH radical in a slit supersonic jet: Vibration-rotation-tunneling dynamics in the symmetric CH stretch manifold

In this paper, the sub-Doppler CH-symmetric stretch (ν 3) infrared absorption spectrum of a hydroxymethyl (CH 2OH) radical is observed and analyzed with the radical formed in a slit-jet supersonic discharge expansion (T rot = 18 K) via Cl atom mediated H atom abstraction from methanol. The high sensitivity of the spectrometer and reduced spectral congestion associated with the cooled expansion enable first infrared spectroscopic observation of hydroxymethyl transitions from both ± symmetry tunneling states resulting from large amplitude COH torsional motion. Nuclear spin statistics due to exchange of the two methyl H-atoms aid in unambiguous rovibrational assignment of two A-type K a = 0 ← 0 and K a = 1 ← 1 bands out of each ± tunneling state, with additional spectral information obtained from spin-rotation splittings in P, Q, and R branch K a = 1 ← 1 transitions that become resolved at low N. A high level ab initio potential surface (CCSD(T)-f12b/cc-pvnzf12 (n = 2,3)/CBS) is calculated in the large amplitude COH torsional and CH 2 wag coordinates, which in the adiabatic approximation and with zero point correction predicts ground state tunneling splittings in good qualitative agreement with experiment. Finally, of particular astrochemical interest, a combinedmore » fit of the present infrared ground state combination differences with recently reported millimeter-wave frequencies permits the determination of improved accuracy rotational constants for the ground vibrational state, which will facilitate ongoing millimeter/microwave searches for a hydroxymethyl radical in the interstellar medium.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Univ. of Colorado, Boulder, CO (United States). JILA. National Inst. of Standards and Technology. Dept. of Chemistry and Biochemistry
Publication Date:
Grant/Contract Number:
FG02-09ER16021; SC0002123
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 19; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Colorado, Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; chemical compounds and components; vibrational states; infrared spectroscopy; chemical elements; rotational spectra; adiabatic theorem; supersonics; interstellar medium; potential energy surfaces
OSTI Identifier:
1474104

Schuder, Michael D., Wang, Fang, Chang, Chih-Hsuan, and Nesbitt, David J.. Sub-Doppler infrared spectroscopy of CH2OH radical in a slit supersonic jet: Vibration-rotation-tunneling dynamics in the symmetric CH stretch manifold. United States: N. p., Web. doi:10.1063/1.4982803.
Schuder, Michael D., Wang, Fang, Chang, Chih-Hsuan, & Nesbitt, David J.. Sub-Doppler infrared spectroscopy of CH2OH radical in a slit supersonic jet: Vibration-rotation-tunneling dynamics in the symmetric CH stretch manifold. United States. doi:10.1063/1.4982803.
Schuder, Michael D., Wang, Fang, Chang, Chih-Hsuan, and Nesbitt, David J.. 2017. "Sub-Doppler infrared spectroscopy of CH2OH radical in a slit supersonic jet: Vibration-rotation-tunneling dynamics in the symmetric CH stretch manifold". United States. doi:10.1063/1.4982803. https://www.osti.gov/servlets/purl/1474104.
@article{osti_1474104,
title = {Sub-Doppler infrared spectroscopy of CH2OH radical in a slit supersonic jet: Vibration-rotation-tunneling dynamics in the symmetric CH stretch manifold},
author = {Schuder, Michael D. and Wang, Fang and Chang, Chih-Hsuan and Nesbitt, David J.},
abstractNote = {In this paper, the sub-Doppler CH-symmetric stretch (ν3) infrared absorption spectrum of a hydroxymethyl (CH2OH) radical is observed and analyzed with the radical formed in a slit-jet supersonic discharge expansion (Trot = 18 K) via Cl atom mediated H atom abstraction from methanol. The high sensitivity of the spectrometer and reduced spectral congestion associated with the cooled expansion enable first infrared spectroscopic observation of hydroxymethyl transitions from both ± symmetry tunneling states resulting from large amplitude COH torsional motion. Nuclear spin statistics due to exchange of the two methyl H-atoms aid in unambiguous rovibrational assignment of two A-type Ka = 0 ← 0 and Ka = 1 ← 1 bands out of each ± tunneling state, with additional spectral information obtained from spin-rotation splittings in P, Q, and R branch Ka = 1 ← 1 transitions that become resolved at low N. A high level ab initio potential surface (CCSD(T)-f12b/cc-pvnzf12 (n = 2,3)/CBS) is calculated in the large amplitude COH torsional and CH2 wag coordinates, which in the adiabatic approximation and with zero point correction predicts ground state tunneling splittings in good qualitative agreement with experiment. Finally, of particular astrochemical interest, a combined fit of the present infrared ground state combination differences with recently reported millimeter-wave frequencies permits the determination of improved accuracy rotational constants for the ground vibrational state, which will facilitate ongoing millimeter/microwave searches for a hydroxymethyl radical in the interstellar medium.},
doi = {10.1063/1.4982803},
journal = {Journal of Chemical Physics},
number = 19,
volume = 146,
place = {United States},
year = {2017},
month = {5}
}