The Pressure Broadening of the Vibration Rotation Band of the HCN Molecule at 10380 A.

The relation between the line-width of the 0-3 vibration-rotation band of HCN at 10380 Å. and the pressure of the HCN gas, as well as the pressure resulting from the addition of different extraneous gases, was investigated. In the P and R branches of the band a relation was found between the half-line width and the rotational quantum number, J , which differs for the broadening due to self-pressure and the broadening resulting from pressure of extraneous gases. The results could be explained, according to London's theory, in the former case as an effect due to the combined action of rotational resonance alignment, and in the latter case to alignment alone. Measurements made with the addition of DCN suggest that the chain association of the hydrogen bridge bonds also has an effect on the half-width value.