First Observation Of The Spin Rotational Structure Of The Hydroxymethyl Radical (h2coh) In The Ch2 Asymmetric Mode

Chang, Chih-Hsuan

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https://hdl.handle.net/2142/50829 Copy

Description

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

Issue Date

2014-06-19

Keyword(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.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50829

DOI

https://doi.org/10.15278/isms.2014.RJ10

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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