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A prism of cesium bromide has been installed in a P erkins-Elmer spectrometcr, and s pe c~ra have bee n obse rved 111 t he regIOn from 15 to 38 1-' . This prism is of better optical quahty than those of I(RS-5, which makes it poss ible to obtain s harp images at t he s~cond s il t of t he spec trom ete r. M easurements have been made with t his cesium bromide prism , which has a refracting angle of 55 , and the results have been compared with those obtained with a 26 KRS-5 prism. The dispersion of cesium bromide from 15 to 38 I-' is about eq ual to I{RS-5, but the effective resolution is about twice as great. A group of rota tional lines of water vapor at 28.4 I-' is now clearl y resolved into three components, t.he two narrow ones being se parated by 1.8 cm -I. The lo ng wavelength bands of carbon di s ulfide and chloroform have bee n measured in the vapor s tate, and it is possible, with t he good definition availabl?, to observe the P , ()'. and R branches. In the spectral region bcyond 33 1-' , t he stray radlat.lon produccs a co nsid erab le amou nt of t he total de flection. The stray radiation was r edu ced to one-tenth of its value by t he use of a rou ghe ned silver mirror located in t he sou rce bo x of t he spectrometer.
Plyler et al. (Fri,) studied this question.