TORSIONAL EXCITATION IN O-H STRETCH OVERTONE SPECTRA OF ETHYL HYDROPEROXIDE CONFORMERS Shizuka...
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Transcript of TORSIONAL EXCITATION IN O-H STRETCH OVERTONE SPECTRA OF ETHYL HYDROPEROXIDE CONFORMERS Shizuka...
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
Atmospheric hydroperoxide formation
Reeves and Penkett. Chem. Rev. 103, 5199 (2003)Lee et al. Atmos. Environ. 34, 34775 (2000)
High NO Low NO
Aldehyde
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
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
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
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
** * *
**
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
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
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
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
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
** * *
**
Acknowledgements
Katy Meek Ma Thida Lauren Owen Margaret Nyamumbo
Camille & Henry Dreyfus FoundationNational Science Foundation
Smith College
Calculated O-H stretch frequencies
Calculated dissociation energy
Hou et al. J. Phys. Chem. 109, 112 (2005)
Calculated D0 = 41.6 kcal mol-1
OH radicals from O-H stretch overtone excitation
4nOH
6nOH
5nOH
Wavelength (nm)
Figure adapted from Matthews, Sinha and Francisco, PNAS 102, 7449 (2005)