High-resolution Fourier transform infrared study of the out-of-plane bending fundamentals of HCOCl and DCOCl

High-resolution infrared spectra of the out-of-plane bending (upsilon(6)) fundamentals of the transient molecules HCOCl and DCOCl are reported. The HCOCl band consists of a C-type component due to the out-of-plane transition moment from the ground state and a Coriolis-induced parallel component which derives its intensity from mixing of the 4(1) and 6(1) vibrational states. In DCOCl, the C-type component is absent, so that all of the band intensity comes from Coriolis-induced borrowing from upsilon(4). The DCOCl upsilon(4) and upsilon(6) bands have been fitted simultaneously to account for the strong first-order and weaker second-order a-axis Coriolis interactions between the fundamentals. In HCOCl the upsilon(6) band is only weakly perturbed by upsilon(4) but is more strongly affected by local interactions with the 5(2) vibrational level, which have been explicitly included in the analysis. Ab initio predictions of the relative intensities of the upsilon(6) fundamentals show that the change in dipole moment is much smaller for DCOCl, accounting for the absence of the C-type component. (C) 1995 Academic Press, Inc.