Deperturbation of the low-frequency infrared modes of ketene (CH2CO)

In this paper we report an asymmetric rotor analysis of the room temperatur e Fourier-transform infrared gas phase spectrum of ketene (CH2CO) at near D oppler limited resolution. The four fundamental modes below 1000 cm(-1) (nu (5),nu(6),nu(8) and nu(9)) are influenced by global z-axis Coriolis perturb ations. Using a general non-linear least-squares fitting program developed at the ETH Zurich to determine perturbation parameters and deperturbed mole cular constants we have re-analysed the FTIR spectrum to free the effective rotational constants from Coriolis contributions. First-order z-axis Corio lis zeta constants connecting the above four fundamentals were determined. Strong local perturbations for the K-a' = 0 and 1 states are observed for t he nu(8) vibrational stare. (C) 2000 Elsevier Science B.V. All rights reser ved.