The Near Infra-Red Absorption Spectra of Calcite and Strontianite

Abstract

A study of the near infra-red absorption spectra of calcite and strontianite has been made by using thick specimens. With a specimen 2 cm thick, cut at right angles to the optic axis, bands were observed for calcite at 1.76μ, 1.90μ, 2.00μ and 2.20μ. These bands have the same characteristics as those observed by Schaefer, Bermuth and Matossi in the near infra-red. The second order equations have been applied to the bands observed in this work and to those observed by Schaefer and it was found that series relationships existed between them with only small deviations of the observed from the calculated values. In strontianite a similar set of bands was observed at 1.89μ, 2.01μ and 2.19μ, and they were of the same type as those for calcite. The value of the inactive fundamental was calculated and found to correspond to a band at 9.2μ, which is in good agreement with the value of 8.98μ found theoretically by Nielsen.