Vibration–Rotation Bands of Deuterium Cyanide and Hydrogen Cyanide*

Abstract

Six vibration–rotation bands of DCN between 2 and 6 μ have been analyzed. All the rotational constants have been obtained through the terms quadratic in vibrational quantum numbers. Two quadratic and seven cubic vibrational anharmonic constants have been obtained explicitly. Seven combinations of quadratic and cubic vibrational constants have also been obtained. Data are given on the analysis of the two parallel fundamental bands of D¹³CN, as well as the ν₃ bands of DC¹⁵N, H^I3CN, and HC¹⁵N. Δ–Δ transitions of both DCN and HCN in the ν₃ fundamental regions have been analyzed. The splitting of the Δ levels was clearly observed for the first time and is in agreement with the l-type resonance calculations. The line structure of the Q branches of both Π–Π and Δ–Δ “hot bands” has also been resolved. By means of the Ritz principle the levels 2ν₂⁰, 2ν₂², and ν₂¹ of DCN and 2ν₂² of HCN have been determined.