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 Title: First Observation Of The Spin Rotational Structure Of The Hydroxymethyl Radical (h2coh) In The Ch2 Asymmetric Mode Author(s): Chang, Chih-Hsuan Contributor(s): Nesbitt, David; Wang, Fang Subject(s): Large amplitude motions, internal rotation Abstract: Rotationally-resolved direct infrared absorption spectra of hydroxymethyl radical (H$_{2}$COH) in the CH$_{2}$ asymmetric mode (\nub{2}) were observed for the first time using the Boulder difference frequency generation infrared spectrometer. Hydroxymethyl radical was formed with chemical selectivity via the reaction of Cl radical with CH$_{3}$OH in a discharge slit-jet supersonic expansion. As a result of sub-Doppler linewidth and low rotational temperature, the \textit{b}-type rotational structure and spin-rotation splitting were fully resolved. In particular, tunneling splitting was observed due to the large-amplitude COH torsional mode. Because of the feasible permutation of hydrogens in the methylenic group, nuclear spin intensity alternation was given as: 3:1 for \textit{K$_{a}$}=even, odd in the 0$^{+}$ level, and 1:3 for \textit{K$_{a}$}=even, odd in the 0$^{-}$ level of the ground vibrational state. The assignments were confirmed rigorously by four-line ground state combination differences, which agreed within the experimental frequency uncertainty (10 MHz). The identified transitions were fit with a Watson \textit{A}-reduction Hamiltonian including the spin rotational interaction, leading to unambiguous determination of asymmetric top spectroscopic constants, as well as spin rotational constants ($\epsilon$$_{aa}, \epsilon$$_{bb}$, $\epsilon$$_{cc}$) for the first time. Issue Date: 2014-06-19 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Chang, C.; Nesbitt, D.; Wang, F. FIRST OBSERVATION OF THE SPIN ROTATIONAL STRUCTURE OF THE HYDROXYMETHYL RADICAL (H2COH) IN THE CH2 ASYMMETRIC MODE. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.RJ10 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/50829 DOI: 10.15278/isms.2014.RJ10 Rights Information: Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/ Date Available in IDEALS: 2014-09-172015-04-14
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