The Infrared Spectrum of CN in Its Ground Electronic State

Abstract

12C14N vibration-rotation bands for the sequences (1-0) through (9-8) were observed in the spectral region 1800-2200 cm-1 using a Bruker 120 HR Fourier transform spectrometer at an unapodized resolution of 0.027 cm-1. Of the 362 lines observed, the wavenumbers of 237 lines were least-squares fitted using the Dunham expansion coefficients with a root-mean-square deviation of 0.00093 cm-1. Together with most accurate data from the literature, the data were also fitted in the framework of the reduced potential curve (RPC) method. The global potential energy function resulting from this fit provides a fairly quantitative description of the experimental data, at least up to 30 000 cm-1. In addition to global fitting, the RPC approach was also used for fully quantitative fitting of the data pertaining to the lowest three vibrational states. The effective potential energy curves obtained in this way allow for very accurate predictions of highly excited rotational states.