THE Ã-~X ELECTRONIC TRANSITION OF CH2IOO RADICAL IN THE NEAR INFRARED REGION

Huang, Meng

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https://hdl.handle.net/2142/79135 Copy

Description

Title

THE Ã-~X ELECTRONIC TRANSITION OF CH2IOO RADICAL IN THE NEAR INFRARED REGION

Author(s)

Huang, Meng

Contributor(s)

• Dawes, Richard
• Lolur, Phalgun
• Miller, Terry A.
• Kline, Neal

Issue Date

26-Jun-15

Keyword(s)

Atmospheric science

Abstract

In the past few years, the photolysis of CH$_2$I$_2$ in the presence of O$_2$ has received much attention. It has been shown to be an attractive method for producing the Criegee intermediate, CH$_2$O$_2$. Under certain conditions the reaction is also expected to produce the iodomethyl peroxy radical, CH$_2$IO$_2$. Interestingly both species are expected to have electronic transitions in the near infrared (NIR). The transition in CH$_2$O$_2$ would be analogous to the $tilde{a}-tilde{X}$ singlet-triplet transition in O$_3$ and a NIR $tilde{A}-tilde{X}$ transition in well-known to be characteristic of peroxy radicals. Notwithstanding the above, NIR spectra have not been reported for either CH$_2$O$_2$ or CH$_2$IO$_2$. Based upon these considerations, we have performed the CH$_2$I$_2$ photolysis with O$_2$ in the optical cavity of our room temperature cavity ringdown spectrometer and have discovered a spectrum in the NIR. Our recorded spectrum stretches from a complex origin structure at $approx$6800 wn to beyond 9000 wn. Aside from the origin its strongest feature is a similar, complex band $approx$870 wn to the blue of it, which is likely an O-O stretch vibrational transition, which is present in peroxy radicals but might also be expected for CH$_2$O$_2$. With the aid of high-level {em ab initio} calculations (described in detail in the subsequent talk) we have undertaken the analysis of the spectrum. We find that a spectral analysis, including a number of hot bands arising from populated torsional levels, is consistent with the electronic structure calculations for the $tilde{A}$ and $tilde{X}$ states of CH$_2$IO$_2$.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79135

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