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Title: UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical

Here, the hydroxyl radical (OH) is a key oxidant in atmospheric and combustion chemistry. Recently, a sensitive and state-selective ionization method has been developed for detection of the OH radical that utilizes UV excitation on the A 2Σ +–X 2Π transition followed by fixed 118 nm vacuum ultraviolet (VUV) radiation to access autoionizing. The present study uses tunable VUV radiation generated by four-wave mixing to examine the origin of the enhanced ionization efficiency observed for OH radicals prepared in specific A 2Σ + intermediate levels. The enhancement is shown to arise from resonant excitation to distinct rotational and fine structure levels of two newly identified 2Π Rydberg states with an A3Π cationic core and a 3 d electron followed by ionization. Spectroscopic constants are derived and effects due to uncoupling of the Rydberg electron are revealed for the OH 2Π Rydberg states. The linewidths indicate a Rydberg state lifetime due to autoionization on the order of a picosecond.
Authors:
 [1] ; ORCiD logo [1] ;  [1]
  1. Univ. of Pennsylvania, Philadelphia, PA (United States)
Publication Date:
Grant/Contract Number:
FG02-87ER13792
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 18; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Pennsylvania, Philadelphia, PA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS
OSTI Identifier:
1471072
Alternate Identifier(s):
OSTI ID: 1253065

Green, Amy M., Liu, Fang, and Lester, Marsha I.. UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical. United States: N. p., Web. doi:10.1063/1.4948640.
Green, Amy M., Liu, Fang, & Lester, Marsha I.. UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical. United States. doi:10.1063/1.4948640.
Green, Amy M., Liu, Fang, and Lester, Marsha I.. 2016. "UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical". United States. doi:10.1063/1.4948640. https://www.osti.gov/servlets/purl/1471072.
@article{osti_1471072,
title = {UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical},
author = {Green, Amy M. and Liu, Fang and Lester, Marsha I.},
abstractNote = {Here, the hydroxyl radical (OH) is a key oxidant in atmospheric and combustion chemistry. Recently, a sensitive and state-selective ionization method has been developed for detection of the OH radical that utilizes UV excitation on the A2Σ+–X2Π transition followed by fixed 118 nm vacuum ultraviolet (VUV) radiation to access autoionizing. The present study uses tunable VUV radiation generated by four-wave mixing to examine the origin of the enhanced ionization efficiency observed for OH radicals prepared in specific A2Σ+ intermediate levels. The enhancement is shown to arise from resonant excitation to distinct rotational and fine structure levels of two newly identified 2Π Rydberg states with an A3Π cationic core and a 3d electron followed by ionization. Spectroscopic constants are derived and effects due to uncoupling of the Rydberg electron are revealed for the OH 2Π Rydberg states. The linewidths indicate a Rydberg state lifetime due to autoionization on the order of a picosecond.},
doi = {10.1063/1.4948640},
journal = {Journal of Chemical Physics},
number = 18,
volume = 144,
place = {United States},
year = {2016},
month = {5}
}