Effects of torsion on O-H stretch overtone spectra and direct overtone photolysis of methyl hydroperoxide

Journal Article · Thu Dec 15 04:00:00 EST 2005 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2139673· OSTI ID:20783196

Haynes, Laura M; Vogelhuber, Kristen M; Pippen, Jessica L; Hsieh, Shizuka ^[1]

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1. Chemistry Department, Smith College, Clark Science Center, Northampton, Massachusetts 01063 (United States)

We use laser photoacoustic spectroscopy to obtain overtone spectra at three through six quanta of O-H stretch excitation (3{nu}{sub OH}-6{nu}{sub OH}) for methyl hydroperoxide (MeOOH). Extending the spectral regions beyond our previous work reveals new features that can be attributed to transitions involving torsion about the O-O bond. Experimental spectral profiles (3{nu}{sub OH}-6{nu}{sub OH}) and cross sections (3{nu}{sub OH}-5{nu}{sub OH}) at room temperature show a good agreement with the simulated spectra that we obtain from ab initio calculations employing a vibration-torsion model at 298 K. A Birge-Sponer analysis yields experimental values for the O-H stretch frequency ({omega}=3773{+-}15 cm{sup -1}) and anharmonicity ({omega}x=94{+-}3 cm{sup -1}). We also detect OH radicals by laser-induced fluorescence and present photodissociation action spectra of MeOOH in the regions of 4{nu}{sub OH} and 5{nu}{sub OH}. While the spectral profile at 5{nu}{sub OH} mimics the photoacoustic spectrum, the peak intensity for transitions to torsionally excited states is relatively more intense in the action spectrum at 4{nu}{sub OH}, reflecting the fact that the 4{nu}{sub OH} excitation energy is below the literature dissociation energy (D{sub 0}=42.6{+-}1 kcal mol{sup -1}) so that features in the action spectrum come from thermally populated excited states. Finally, we use our calculations to assign contributions to individual peaks in the room-temperature spectra and relate our findings to a recent dynamics study in the literature.

• OSTI ID: 20783196
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 23 Vol. 123; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
CROSS SECTIONS
DISSOCIATION
DISSOCIATION ENERGY
EXCITATION
FLUORESCENCE
HYDROXYL RADICALS
ORGANIC COMPOUNDS
PHOTOACOUSTIC SPECTROSCOPY
PHOTOLYSIS
SPECTRA
TEMPERATURE RANGE 0273-0400 K
TORSION
VIBRATIONAL STATES