Sub-doppler infrared spectroscopy of jet cooled CH2Br radical: CH2 stretch vibrations

Scrape, Preston G.

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https://hdl.handle.net/2142/100498 Copy

Description

Title

Sub-doppler infrared spectroscopy of jet cooled CH2Br radical: CH2 stretch vibrations

Author(s)

Scrape, Preston G.

Contributor(s)

• Nesbitt, David
• Lesko, Daniel
• Kortyna, Andrew

Issue Date

2018-06-18

Keyword(s)

Radicals

Abstract

Bromomethyl radical (CH2Br) has recently been used as a novel precursor for producing the simplest Criegee intermediates (CH2OO). With the goal of spectroscopically investigating a Criegee intermediate, we have pursued high resolution characterization of the CH2Br radical in our slit jet discharge spectrometer. The bromomethyl radical is generated by seeding CH2Br2 into a Ne/He/H2 mixture in a pulsed slit discharge. The radical is produced through either electron dissociative attachment to form bromine anions or hydrogen abstraction of bromine, with subsequent cooling in a supersonic expansion to about 15 K. Infrared absorption in the CH2 symmetric stretch vibrational band is fully resolved at high single-to-noise ratios for both the 79Br and 81Br isotopologues . The sub-Doppler rotational structure is fitted to a rigid-rotor Hamiltonian with spin-rotation coupling, generating principal rotational constants and the spin-orbit coupling tensor for the vibrationally excited state. The results are consistent with a vibrationally averaged planar π-radical with unpaired electron spin density in a partially filled pπ-orbital on the central C atom. Relative band intensities in the symmetric and antisymmetric CH2 stretch manifolds provide further elucidation of the ”charge-sloshing” mechanism noted in CH2F, CH2Cl, and CH2I radical species due to vibrationally mediated shifts in electron density along the carbon-halogen bond axis.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100498

DOI

10.15278/isms.2018.MJ08

Copyright and License Information

Copyright 2018 Preston G. Scrape

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