UV + VUV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical
- Univ. of Pennsylvania, Philadelphia, PA (United States)
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.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia, PA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Contributing Organization:
- Argonne National Laboratory; Cardiff University
- Grant/Contract Number:
- FG02-87ER13792
- OSTI ID:
- 1471072
- Alternate ID(s):
- OSTI ID: 1253065
- Journal Information:
- Journal of Chemical Physics, Vol. 144, Issue 18; ISSN 0021-9606
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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