Sunghwan Kim - Density functional calculations, structure, and vibrational frequencies of 2-cyclopenten-1-one in its S0, S1(n,π*), T1(n,π*), and T2(π,π*) states

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  Publication Details (including relevant citation   information):

  J. Choo, S. Kim,   S. Drucker, and J. Laane;

  Journal of Physical Chemistry A,   2003107, 10655.



  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 spectroscopy described in the previous paper.   Structures and vibrational frequencies were calculated for each   state at both the B3LYP/6-31+G(d,p) and B3LYP/6-311+G(d,p)   levels. The structural information was used to obtain the kinetic   energy part of the ring-bending Hamiltonian, for the analysis of   triplet-state spectral data. The density functional calculations   show the molecule in its S0 and S1 states to be planar, but to   have a small barrier to planarity in the T1(n,π*) triplet state.   This is in line with potential-energy fits to the experimental   ring-bending levels for each state. The calculated barrier for   the T2(π,π*) state is 999 cm-1. This provides further   confirmation that the cavity ringdown data, from which a 43-cm-1   barrier was determined, correspond to the T1(n,π*) state. The   calculated vibrational frequencies are in excellent agreement   with the experimental data for the S0 state and also for the most   part for the S1 and T1 states. Notably, the frequency calculated   for the very anharmonic ring-bending vibration cannot be expected   to be very accurate.


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