Near-Infrared Spectrum of the A2Πi–X2Σ+ (2,0) Band of CN Studied by Concentration Modulation Laser Spectroscopy

The rotational structure of (2,0) vibrational band of A2Πi–X2Σ+ transition of CN has been studied by concentration-modulation laser spectroscopy using a Ti:sapphire laser. The CN radical was produced in the ac glow discharge of acetonitrile with helium as the carrier gas. All 12 branches including four new branches have been observed and measured with an absolute accuracy of 0.007 cm−1 in the region 12 450–12 750 cm−1. Analysis of the spectra has led to improved molecular parameters of the A2Πi (v′ = 2) state.