Infrared Absorption of Zinc Oxide and of Adsorbed CO2. I

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Abstract
For measuring the absorption spectra of a powdered solid in contact with a gas and adsorbed gas molecules, a new disk technique has been developed by which the powder can be formed into optical samples having sufficiently high transmissivity and a well‐defined thickness. By the use of this technique the spectrum of zinc oxide under varying heat treatments and gaseous conditions was studied at 20° and 300°C mainly in the region 2000∼1200 cm—1. With samples made from zinc nitrate and evacuated at 300°C a distinct symmetrical band was observed at 1550 cm—1 which was investigated in detail. From its intensity, behavior, and correlation with absorption by free electrons, the band was attributed to an electronic absorption associated with zinc vacancies in the crystal lattice. Samples made from zinc carbonate showed strong absorption by free electrons on being evacuated, affording a useful basis for observing its variation.