High-resolution FTIR study and rotational analyses of the ν1- ν5 bands of ethynyl isocyanide: HCCNC and DCCNC

Abstract

Fourier transform infrared spectra of HCCNC and DCCNC have been recorded in the 350 to 5000 cm −1 and 350 to 3500 cm −1 ranges, respectively, with a typical resolution of 4 × 10 −3 cm −1. The fundamentals ν 1- ν 5 as well as several combination bands and overtones have been observed. Ground state and excited state parameters have been determined from rotational analyses, hot bands with ν 7 providing data on the v 7 = 1 state. Standard deviations of fits of more than 4000 experimental data ranged from 1 to 10 × 10 −4 cm −1. Several local perturbations have been detected. A major anharmonic perturbation by the v 5 = 2 0 and v 6 = 2 0 levels affects the ν 4 vibration in both isotopomers, and a deperturbation has been performed. For HCCNC, a rotational perturbation of the v 5 = 1 state, presumably by v 7 = 3 levels, is evident. The experimental parameters show excellent agreement with those recently obtained for HCCNC by millimeter-wave spectroscopy and with the results of concomitant ab initio calculations by Botschwina and co-workers.