Ultraviolet cavity ringdown spectra of 2-cyclohexen-1-one and its potential energy function and structure for the electronic ground state

Abstract

The S-1(n,pi*) <-- S-0 cavity ringdown spectrum of 2-cyclohexen-1-one vapor has been recorded in the vicinity of the 0(0)(0) band, which is at 26 089.1 cm(-1). Observation of hot bands in the spectrum has permitted the determination of several low-frequency fundamentals and overtones in the ground electronic state. The lowest two excited quantum states for the inversion vibration (v(39)) were found to be at 99.0 and 197.0 cm(-1). Together with previously published far-IR spectra and vapor-phase Raman spectra, the fundamental frequencies for v(39), v(38), and v(37) have been determined. From observed v(39) levels, the barrier to inversion has been determined experimentally to be 1900 +/- 300 cm(-1), which is very different from values of 935 and 3379 cm(-1) previously reported from Raman and far-IR data, respectively. Density functional calculations carried out in this paper give a barrier value of 2090 cm(-1) when the B3LYP/6-311+G(d,p) basis set is used.