Experimental

Abstract

The infrared absorption spectra were investigated with the double-beam instrument designed in the Institute of Physics of the Academy of Sciences by Malyshev, Markov, and Shubin [13–15]. The design and characteristics of the instrument and the special techniques in its use are not discussed here, as good and accurate accounts are given in the papers cited above and in [4]. It may be added that, in addition to NaCl and KBr prisms which were used for studying infrared absorption spectra in the range from 2 to 24 μ, we used the KRS-5 prism (a mixture of thallium bromide and iodide crystals) for obtaining absorption spectra in the far infrared region, from 24 to 36 μ. It should be pointed out that, apart from its mechanical weakness, this prism has another very significant fault: the reflection coefficient is very large. The cesium iodide prism has better optical characteristics than KRS-5, but as it was not available all our investigations were conducted with the KRS-5 prism.