Ethyl + O2 in Helium Nanodroplets: Infrared Spectroscopy of the Ethylperoxy Radical
| Autor: | Gary E. Douberly, Christopher P. Moradi, Joseph T. Brice, Henry F. Schaefer, Peter R. Franke |
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| Rok vydání: | 2019 |
| Předmět: |
010304 chemical physics
Chemistry Infrared Radical chemistry.chemical_element Infrared spectroscopy 010402 general chemistry 01 natural sciences Molecular physics 0104 chemical sciences Normal mode 0103 physical sciences Physical and Theoretical Chemistry Spectroscopy Conformational isomerism Basis set Helium |
| Zdroj: | The Journal of Physical Chemistry A. 123:3558-3568 |
| ISSN: | 1520-5215 1089-5639 |
| Popis: | Helium-solvated ethylperoxy radicals (CH3CH2OO•) are formed via the in situ reaction between 2A' ethyl radical and 3Σg- 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 C1 gauche and C s trans rotamers in an approximate 2:1 ratio; this is despite the prediction that the gauche rotamer lies 44 cm-1 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. |
| Databáze: | OpenAIRE |
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