Pressure-Induced Fundamental Infrared Absorption Band of Gaseous Chlorine

The pressure-induced fundamental infrared absorption band of chlorine gas at 298° and 369°K has been investigated. The frequency of the maximum absorption of the band has been found to agree with that calculated for the free molecule when the effects of the three isotopic species 35Cl2, and 35Cl 37Cl, and 37Cl2 are considered. The binary absorption coefficient has been measured and using it with the theory of Van Kranendonk a value of 57a02 ± 25% has been derived for the rate of change of polarizability with internuclear distance. The temperature dependence of the binary absorption coefficient indicates the possible presence of bound states (Cl2)2 at room temperature.