1. Ultraviolet Cavity Ringdown Spectra of 2-Cyclohexen-1-one and its Inversion Potential Energy Function
Mohamed Rishard, Emily Giles, Jaeboom Choo, Daniel Autrey, Stephen Drucker, Jaan Laane
June

2. Outline
Introduction
Previous spectroscopic studies on 2-cyclohexen-1-one (2CHO)
Cavity ringdown spectra of 2CHO
Inversion potential energy function of 2CHO in the ground electronic (S0) state
Conclusions and present research work

3. 2-Cyclohexen-1-one An asymmetric six-membered non-planar ring molecule
Mol. Weight = g/mol
Boiling point = C (at 1 atm)
Vapor pressure = ~1.8 torr (at 250C)
An asymmetric six-membered non-planar ring molecule
Microwave studies by Manley and Tyler in 1970 proposed a structure which only C-5 was significantly out-of-plane
The conjugation between C=C and C=O groups is expected to provide extra rigidity to the ring

4. Out-of- plane vibrations of 2CHO

5. Previous spectroscopic studies: Vapor Raman spectra
L. A. Carreira, T.G. Towns, T. B. Malloy, J. Chem. Phys., 70(5), 2273, (1979)

6. Previous spectroscopic studies: far-IR spectra
T. L. Smithson, H. Wieser, J. Chem. Phys., 73(5), 2518, (1980)

7. Previous spectroscopic studies: far-IR spectra
T. L. Smithson, H. Wieser, J. Chem. Phys., 73(5), 2518, (1980)

8. Cavity Ringdown Spectroscopy-Experimental
Cavity Ring-Down Spectroscopy, Andrew Orr-Ewing, Mike Ashfold

9. CRDS spectra of 2CHO
Relative wavenumbers of 2CHO with respect to the S1 band origin (Res. 0.1 cm-1)

10. Calculated and experimental Raman spectra of 2CHO

11. Vibrational assignments of 2CHO
(Frquencies are in cm-1)
Observed by CRDS Calculateda Inferred Assignment b b b c b
a From b3lyp/6-311+g(d,p) calculation
b Inferred from far-IR data
C From the current vapor Raman spectrum

12. Vibrational energy levels for the ground state (S0) of 2CHO

13. Ring inversion potential
Potential energy function: V = x 102 S2 – x 103 S4 Barrier to planarity = cm-1 (calculated barrier-to-planarity by DFT methods = 2090 cm-1)

14. Conclusions and present work
Previous Raman and IR studies misinterpreted the spectra and miscalculated the inversion barrier.
CRDS spectra have allowed us to clarify the vibrational levels of low-frequency vibrations
The experimental value of cm-1 for the barrier to planarity agrees very well with the value of 2090 cm-1 determined by DFT calculations
The large uncertainty value came from the extrapolation of the P.E. function above the experimental values.
Determination of inversion barriers of S1 and T1 states and also for the 2,2,6-deuterated isotopomer of 2CHO is currently being carried out

15. Acknowledgement$ National Science Foundation
Robert A. Welch Foundation
Texas Advanced Research Program