Integrated intensities for some infrared absorption bands of HCN

The integrated intensities of several vibrational bands of HCN have been measured using a Fourier transform infrared spectrometer. The experiments yield the following values for the integrated intensities in cm–2 atm–1 at 298 K: ν3, 255 ± 11; 2ν2, 34.7 ± 0.9; ν2+ν3, 4.8 ± 0.4; ν1+ν2, 2.9 ± 0.3; ν3–ν2, 0.51 ± 0.04. The spectra also reveal that much of the weak absorption between 2200 and 2000 cm–1 is due to the 3ν2 band and to a band of the (HCN)2 dimer. The imegrated intensity of the ν1 band is estimated to be only ca. 0.1 cm–2 atm–1.