Infrared Spectroscopy of Surface Films and Powders Using a Metal Light Pipe (Experimental)

Abstract

Light pipe infrared spectra of adsorbed layers and powders are shown. They are compared with specular external reflection, ATR, KBr pellet transmission, and diffuse reflection spectra. The resultant light pipe spectra are found to obey the predictions of the theory presented in the previous companion paper [Appl. Spectrosc. 41, 46–62 (1987)], including the high sensitivity and S/N predicted to be attainable. They are easy to obtain and to interpret. Only fractions of a milligram of sample are required in favorable cases. The light pipe is convenient as a reaction cell, allowing changing spectra to be followed in real time. In the previous paper were presented equations for absorption spectra of thin layers of material on the inner surface of a light pipe, in the infrared. In the present paper the equations are tested against experimental reality. These tests are a crucial verification of the theory.

The Brass Light Pipe: An Easy Way to Obtain Infrared Spectra of Liquid Films and Monolayers

“…Hansen and collaborators used the light pipe (LP) technique to obtain infrared (IR) spectra of powders, especially of uranium salts. [1][2][3][4] Chapados and collaborators used LP to study the 5 lm and far-infrared (FIR) bands of NH 3 . 5,6 More recently, LPs were used in conjunction with a gas chromatograph to characterize eluents of amphetamines, fatty acids, and nerve gas.…”