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TORSIONAL EXCITATION IN O-H STRETCH OVERTONE SPECTRA OF ETHYL HYDROPEROXIDE CONFORMERS
Shizuka Hsieh, Ma Thida, Margaret Nyamumbo, Hannah Hitchner, Noah Naamad, Kelly Smith, Robert G. Linck
Department of Chemistry, Smith College, Northampton, MA 01063
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Atmospheric hydroperoxide formation
Reeves and Penkett. Chem. Rev. 103, 5199 (2003)Lee et al. Atmos. Environ. 34, 34775 (2000)
High NO Low NO
Aldehyde
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OH radicals from O-H stretch overtone excitation
Closser, Vogelhuber and Hsieh. J. Phys. Chem. A 112, 1238 (2008)
LIF
sign
al
lOvertone
635 625 615 605 595
(nm)LIF
CH3CH2OOH
CH3CH2O + OH
1
2
3
4
5
6
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O-H stretch overtone excitation for 3-6 quanta
Homitsky et al. J. Phys. Chem. A 108, 9492 (2004)
CH3CH2OOH
1
2
3
4
5
6
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Photoacoustic spectra for 3-6 quanta of O-H stretch
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
3nOH 4nOH 5nOH 6nOH
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Photoacoustic spectra for 3-6 quanta of O-H stretch
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
3nOH 4nOH 5nOH 6nOH
** * *
**
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Potentials for O-O torsion
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
Dihedral angle180 180 180 180
Ener
gy (c
m-1
)
3nOH
4nOH
5nOH
6nOH
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Potentials for O-O torsion
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
Dihedral angle180 180 180 180
Ener
gy (c
m-1
)
3nOH
4nOH
5nOH
6nOH
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Simulated absorption spectra (preliminary)
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
3nOH 4nOH 5nOH 6nOH
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Simulated absorption spectra (preliminary)
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
3nOH 4nOH 5nOH 6nOH
Conformer population
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O-H stretch overtone excitation for 3-6 quanta
Wavenumbers (cm-1)
s (1
0-22 cm
2 mol
ecul
e-1)
s (1
0-23 cm
2 mol
ecul
e-1)
s (1
0-24 cm
2 mol
ecul
e-1)
3nOH 4nOH 5nOH 6nOH
** * *
**
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Acknowledgements
Katy Meek Ma Thida Lauren Owen Margaret Nyamumbo
Camille & Henry Dreyfus FoundationNational Science Foundation
Smith College
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Calculated O-H stretch frequencies
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Calculated dissociation energy
Hou et al. J. Phys. Chem. 109, 112 (2005)
Calculated D0 = 41.6 kcal mol-1
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OH radicals from O-H stretch overtone excitation
4nOH
6nOH
5nOH
Wavelength (nm)
Figure adapted from Matthews, Sinha and Francisco, PNAS 102, 7449 (2005)