The 2ν5 Overtone Band of Cyanoacetylene by High Resolution FTIR Spectroscopy

The 2ν₅ overtone band of cyanoacetylene, HCCCN, has been measured with a high resolution FTIR spectrometer. The analysis of the accidental resonances results in very accurate parameters for the observed ν₅ = 2 state as well as for the hidden perturber state (ν₄ = 1, ν₇ = 2); the vibrational energy and the rotational constant have been determined to be 1312.991921(23) cm^-1 and 4552.38440(23) MHz for the ν₅ = 2 state, and 1310.0627(6) cm^-1 and 4572.463(4) MHz for the (ν₄ = 1, ν₇ = 2) state. The associated hot bands from the ν₇ = 1, ν₆ = 1, and ν₅ = 1 state have also been analyzed.