Infrared Spectrum of Carbon Dioxide, Enriched in Oxygen-18

Abstract

The infrared spectrum of a sample of carbon dioxide enriched to about 10 at. % with O¹⁸ was examined in the region 1620–5400 cm^—1, using an Ebert grating spectrometer with spectral slitwidths ranging from 0.2 to 0.4 cm^—1. Ten previously unreported bands were analyzed and assigned to various species of O¹⁸ substituted carbon dioxide and Courtoy's results for C¹²O¹⁶O¹⁸ in the 2‐μ region were confirmed. Courtoy's unexpectedly high value for the Fermi resonance constant of this species was confirmed by the separation of previously unreported Fermi‐resonant bands. The positions of the two bands assigned to C¹²O¹⁸₂ suggest that the resonance constant for this species is larger still. A resonance interaction was found in C¹²O¹⁶O¹⁸, dependent on the potential constant k₁₁₃.