| Title
| - Density Functional Calculations, Structure, and Vibrational Frequencies of2-Cyclopenten-1-one in Its S0, S1(n,π*), T1(n,π*), and T2(π,π*) States
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| Abstract
| - Density functional calculations have been carried out on the S0, S1(n,π*), and T1(n,π*) states of 2-cyclopenten-1-one (2CP) to complement the experimental study of the triplet state using cavity ringdown spectroscopydescribed in the previous paper. Structures and vibrational frequencies were calculated for each state at boththe B3LYP/6-31+G(d,p) and B3LYP/6-311+G(d,p) levels. The structural information was used to obtainthe kinetic energy part of the ring-bending Hamiltonian, for the analysis of triplet-state spectral data. Thedensity functional calculations show the molecule in its S0 and S1 states to be planar, but to have a smallbarrier to planarity in the T1(n,π*) triplet state. This is in line with potential-energy fits to the experimentalring-bending levels for each state. The calculated barrier for the T2(π,π*) state is 999 cm-1. This providesfurther confirmation that the cavity ringdown data, from which a 43-cm-1 barrier was determined, correspondto the T1(n,π*) state. The calculated vibrational frequencies are in excellent agreement with the experimentaldata for the S0 state and also for the most part for the S1 and T1 states. Notably, the frequency calculated forthe very anharmonic ring-bending vibration cannot be expected to be very accurate.
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