Jet‐cooled fluorescence excitation spectrum, carbonyl wagging, and ring‐puckering potential energy functions of 3‐cyclopenten‐1‐one in its S 1 ( n ,π*) electronic excited state
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The jet-cooled fluorescence excitation spectrum of 3-cyclopenten-1-one has been recorded in the 308-330 nm region, and the electronic origin for the S1(n,π*) state of A2symmetry was observed at 30 229 cm-1. The observed spectrum consists of more than 80 bands involving primarily ν3(carbonyl stretch), ν29(carbonyl out-of-plane wagging), and ν30(ring puckering). Bands were also assigned to combinations with seven other vibrational modes. The energies for the ν = 0 to 11 quantum states of ν29were measured and used to determine a one-dimensional potential energy function. This function has energy minima at wagging angles of ±24° and a barrier to inversion of 939 cm-1. Four bands associated with ν30were observed and were used to determine an asymmetric single-minimum one-dimensional ring-puckering potential energy function for the S1(n,π*) state. The ring-puckering energy levels in the ν29vibrational excited states are little changed from the ν = 0 state indicating that there is little interaction between the carbonyl wagging and the ring-puckering motions. © 1995 American Institute of Physics.
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