Jet-cooled fluorescence excitation spectra, conformation, and carbonyl wagging potential energy function of cyclopentanone and its deuterated isotopomers in the S1(n, ?*) electronic excited states

Article abstract of DOI:10.1063/1.464851

The jet-cooled fluorescence excitation spectra of cyclopentanone and its 2,2,5,5-d₄ isotopomer have been recorded in the 305-335 nm region.In addition, the spectra of d₁, d₂, and d₃ species were obtained from isotopic mixtures.The electronic band origin of the d₀ molecule for the S₁ (n, ?^*) state of A₂ symmetry occurs at 30 276 cm^-1, while that of the d₄ molecule is at 30 265 cm^-1.More than 100 fluorescence bands were assigned for each species.These arise from combinations of ν₃ (C=O stretch), ν₁₁ (ring-angle bending), ν₁₈ (ring twisting), ν₂₅ (C=O out-of-plane wag), ν₂₆ (ring bending), and ν₃₆ (C=O in-plane wag) and their vibrational excited states.The vibrational frequencies for ν₃, ν₁₁, and ν₃₆ are significantly lower in the S₁ state than the S₀ ground state.However, the out-of-plane ring modes ν₁₈ and ν₂₆ are only slightly shifted.A progression observed for ν₂₆ does indicate that in the S₁ state, the bent ring conformation lies about 500 cm^-1 above the ring-twisting minimum and corresponds to a saddle point in the two-dimensional ring-twisting/ring-bending potential energy surface.Band progressions for ν₁₈ can be used to calculate the ring-twisting barriers (the barriers to planarity) for the d₀ and d₄ isotopomers to be 1433 and 1240 cm^-1, respectively.Because of limited data, however, these values may be as much as several hundred cm^-1 too high.The energies for the C=O out-of-plane wagging states up to v₂₅ = 9 for each isotopomer were determined for the S₁ state and these were used to calculate the C=O wagging potential energy functions for each.In the S₁ state, the barrier to inversion of the C=O group is 672+/-10 cm^-1 and the wagging angle is 22 deg +/- 1 deg.

Full text of DOI:10.1063/1.464851

Jetcooled fluorescence excitation spectra, conformation, and carbonyl wagging
potential energy function of cyclopentanone and its deuterated isotopomers in the
S 1 (n,π*) electronic excited states
Jian Zhang, WheYi Chiang, and Jaan Laane
Citation: The Journal of Chemical Physics 98, 6129 (1993); doi: 10.1063/1.464851
View online: http://dx.doi.org/10.1063/1.464851
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/98/8?ver=pdfcov
Published by the AIP Publishing
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