Intensities and Widths of the Rovibrational Lines Observed in the 2ν5 Overtone Band of Cyanoacetylene

The relative intensities and Lorentz half-widths of rovibrational transitions observed for the 2ν₅ overtone band of cyanoacetylene, HCCCN, have been determined. The line widths and the intensities were obtained by fitting the observed line profiles with Voigt functions. The Lorentz half-width shows a clear J dependence and vanishes at J ~ 100. In the intensity calculation, we took into account the effects of the accidental resonances between the ν₅ = 2 state and the (ν₄ = 1, ν₇ = 2) state as well as those of the generic l-type resonance. Peak intensities have been found not to be the appropriate presentation of the line intensity because of the strong J dependence of the half-width.