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Ethyl + O 2 in Helium Nanodroplets: Infrared Spectroscopy of the Ethylperoxy Radical.
- Source :
-
The journal of physical chemistry. A [J Phys Chem A] 2019 Apr 25; Vol. 123 (16), pp. 3558-3568. Date of Electronic Publication: 2019 Apr 16. - Publication Year :
- 2019
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Abstract
- Helium-solvated ethylperoxy radicals (CH <subscript>3</subscript> CH <subscript>2</subscript> OO <superscript>•</superscript> ) are formed via the in situ reaction between <superscript>2</superscript> A' ethyl radical and <superscript>3</superscript> Σ <subscript>g</subscript> <superscript>-</superscript> dioxygen. The reactants are captured sequentially through the droplet pick-up technique. Helium droplets are doped with ethyl radical via pyrolysis of di- tert-amyl peroxide or n-propylnitrite in an effusive, low-pressure source. An infrared spectrum of ethylperoxy, in the CH stretching region, is recorded with species-selective droplet beam depletion spectroscopy. Spectral assignments are made via comparisons to second-order vibrational perturbation theory with resonances (VPT2 + K) based on coupled-cluster full quartic force fields. Cubic and quartic force constants, evaluated using a small basis set, are transformed into the normal coordinate system of the higher level quadratic force constants. This transformation procedure eliminates the mismatch between normal modes, which is a source of error whenever normal coordinate force constants from different levels of theory are combined. The spectrum shows signatures of both the C <subscript>1</subscript> gauche and C <subscript>s</subscript> trans rotamers in an approximate 2:1 ratio; this is despite the prediction that the gauche rotamer lies 44 cm <superscript>-1</superscript> lower on the zero-Kelvin enthalpic potential surface for torsional interconversion. Helium droplets are 0.4 K at equilibrium; therefore, in situ ethylperoxy production is highly nonthermal.
Details
- Language :
- English
- ISSN :
- 1520-5215
- Volume :
- 123
- Issue :
- 16
- Database :
- MEDLINE
- Journal :
- The journal of physical chemistry. A
- Publication Type :
- Academic Journal
- Accession number :
- 30946595
- Full Text :
- https://doi.org/10.1021/acs.jpca.9b01867