Rovibronic bands of the (A)over-tilde (2)B(2)<-(X)over-tilde (2)B(1) transition of C(6)H(5)O and C(6)D(5)O detected with cavity ringdown absorption near 1.2 mu m

Abstract

We recorded several rovibronic bands of C(6)H(5)O and C(6)D(5)O in their (A) over tilde (2)B(2)<-(X) over tilde (2)B(1) transitions in the range 1.14-1.31 mu m with the cavity ringdown technique. While the electronic transition is forbidden, several vibronic bands are observed. By comparison of rovibronic contours of observed and simulated bands to determine their types of transition, and by consideration of vibrational wavenumbers of the upper state based on quantum-chemical calculations, we were able to provide vibronic assignments of observed bands and derive several experimental vibrational wavenumbers (given as nu in unit of cm(-1) in this paper) for the (A) over tilde (2)B(2) state, namely, nu(12)=947, nu(13)=793, nu(14)=417, nu(15)=964, nu(16)=866, nu(17)=723, nu(18)=680, and nu(19)=499 for C(6)H(5)O, and nu(12)=772, nu(13)=626, nu(14)=365, nu(15)=812, nu(17)=599, nu(18)=532, and nu(19)=436 for C(6)D(5)O. Transitions involving vibrationally excited levels of nu(20) were also observed; nu(20) of the (A) over tilde state is greater by 50 cm(-1) than the (X) over tilde state of C(6)H(5)O. A weak origin at 7681 cm(-1) for the (A) over tilde <-(X) over tilde transition of C(6)H(5)O (7661 cm(-1) for C(6)D(5)O) with a c-type contour was observed. Observed isotopic ratios of vibrational wavenumbers for the (A) over tilde state of C(6)H(5)O to those of C(6)D(5)O are in good agreement with the predictions from quantum-chemical calculations at the B3LYP/aug-cc-pVTZ level. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2992077]