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Title: Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations

Abstract

A joint experimental and theoretical study is reported on the low-lying vibronic level structure of the ground state of the methoxy radical using slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled, mass-selected anions (cryo-SEVI) and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations. The KDC vibronic model Hamiltonian in the present study was parametrized using high-level quantum chemistry, allowing the assignment of the cryo-SEVI spectra for vibronic levels of CH 3O up to 2000 cm –1 and of CD 3O up to 1500 cm –1 above the vibrational origin, using calculated vibronic wave functions. The adiabatic electron affinities of CH 3O and CD 3O are determined from the cryo-SEVI spectra to be 1.5689 ± 0.0007 eV and 1.5548 ± 0.0007 eV, respectively, demonstrating improved precision compared to previous work. Experimental peak splittings of <10 cm –1 are resolved between the e 1/2 and e 3/2 components of the 6 1 and 5 1 vibronic levels. A pair of spin-vibronic levels at 1638 and 1677 cm –1 were predicted in the calculation as the e 1/2 and e 3/2 components of 6 2 levels and experimentally resolved for the first time. The strong variation of the spin-orbit splittings with a vibrational quantum number ismore » in excellent agreement between theory and experiment. In conclusion, the observation of signals from nominally forbidden a 1 vibronic levels in the cryo-SEVI spectra also provides direct evidence of vibronic coupling between ground and electronically excited states of methoxy.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [4]; ORCiD logo [5]
  1. Univ. of California, Berkeley, CA (United States)
  2. The Johns Hopkins Univ., Baltimore, MD (United States)
  3. Univ. of California, Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Univ. of Florida, Gainesville, FL (United States)
  5. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1369391
Grant/Contract Number:
AC02-76SF00515; CHE-1361031; AC02-05CH11231; FG02-07ER15884
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 22; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Weichman, Marissa L., Cheng, Lan, Kim, Jongjin B., Stanton, John F., and Neumark, Daniel M. Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations. United States: N. p., 2017. Web. doi:10.1063/1.4984963.
Weichman, Marissa L., Cheng, Lan, Kim, Jongjin B., Stanton, John F., & Neumark, Daniel M. Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations. United States. doi:10.1063/1.4984963.
Weichman, Marissa L., Cheng, Lan, Kim, Jongjin B., Stanton, John F., and Neumark, Daniel M. 2017. "Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations". United States. doi:10.1063/1.4984963.
@article{osti_1369391,
title = {Low-lying vibronic level structure of the ground state of the methoxy radical: Slow electron velocity-map imaging (SEVI) spectra and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations},
author = {Weichman, Marissa L. and Cheng, Lan and Kim, Jongjin B. and Stanton, John F. and Neumark, Daniel M.},
abstractNote = {A joint experimental and theoretical study is reported on the low-lying vibronic level structure of the ground state of the methoxy radical using slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled, mass-selected anions (cryo-SEVI) and Köppel-Domcke-Cederbaum (KDC) vibronic Hamiltonian calculations. The KDC vibronic model Hamiltonian in the present study was parametrized using high-level quantum chemistry, allowing the assignment of the cryo-SEVI spectra for vibronic levels of CH3O up to 2000 cm–1 and of CD3O up to 1500 cm–1 above the vibrational origin, using calculated vibronic wave functions. The adiabatic electron affinities of CH3O and CD3O are determined from the cryo-SEVI spectra to be 1.5689 ± 0.0007 eV and 1.5548 ± 0.0007 eV, respectively, demonstrating improved precision compared to previous work. Experimental peak splittings of <10 cm–1 are resolved between the e1/2 and e3/2 components of the 61 and 51 vibronic levels. A pair of spin-vibronic levels at 1638 and 1677 cm–1 were predicted in the calculation as the e1/2 and e3/2 components of 62 levels and experimentally resolved for the first time. The strong variation of the spin-orbit splittings with a vibrational quantum number is in excellent agreement between theory and experiment. In conclusion, the observation of signals from nominally forbidden a1 vibronic levels in the cryo-SEVI spectra also provides direct evidence of vibronic coupling between ground and electronically excited states of methoxy.},
doi = {10.1063/1.4984963},
journal = {Journal of Chemical Physics},
number = 22,
volume = 146,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
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