Transition Dipole Moments for the Vibrational Fundamentals of HNC Determined from the Herman-Wallis Effect

The nu1 and nu3 fundamental bands of HNC are recorded with a Fourier transform infrared spectrometer with a resolution of 0.008 cm-1. Hydrogen isocyanide is generated in situ by dc discharge in a mixture of CH3CN ( approximately 40 mTorr), H2 ( approximately 160 mTorr), and Ar ( approximately 160 mTorr). The transition dipole moments for these fundamental bands are determined from the analysis of the Herman-Wallis effect, and they are compared with ab initio calculated values. It is found that the ab initio values for the nu1 and nu3 bands are about 50 and 30% larger, respectively. The transition dipole moments determined are to be of use for determination of the abundance of HNC in reaction systems such as the dissociative recombination reaction of HCNH+ with electrons. Copyright 1998 Academic Press.