Absorption Cross Sections of Carbon Dioxide and Carbon Monoxide in the Vacuum Ultraviolet

Abstract

Absorption cross sections of CO₂ and CO in the region from 1306 A to 374 A have been measured. The absorption spectrum of CO₂ consists of strong resonance bands between 1306 A and 700 A, with one of them at 923 A showing an unusually large cross section of 117×10^—18 cm². A continuum with bands superimposed on it was observed to start at about 860 A or 14.4 ev which corresponded to the first ionization potential of CO₂. From 700 A toward shorter wavelengths, the contour of the continuum was better defined and smooth with a broad maximum of 36×10^—18 cm² at 550 A and a total f‐value of 4.4. The CO absorption between 1306 A and 955 A was less than 10^—18 cm². Prominent resonance bands appeared at 924 A and extended to 600 A. An absorption continuum could be identified between 876 A and 374 A showing maximum values of σ≃19×10^—18 cm² between 750 A and 550 A with perhaps a small dip of 15×10^—18 cm² at 644 A. The f‐value of this continuum was 2.8.