The Lithium Fluoride Prism in Infra-Red Spectroscopy

Abstract

The performance of a lithium fluoride prism in an infra‐red spectrograph is described. Coverage of the spectral range from 2 to 5.9μ with considerably higher resolving power than that obtainable with rocksalt is demonstrated. Reproductions of the spectra of several hydrocarbon compounds are included which show the high degree of resolution obtained. The methyl group band at 3.37μ is used as an illustration of the value of the apparatus in the study of molecular structure. As a specific example this group is shown to be absent in polystyrene. It is pointed out that lithium fluoride is inferior to fluorite only because it limits observations to wave‐lengths shorter than 5.9μ.