The Absorption of Sunlight by the Earth's Atmosphere in the Remote Infrared Region of the Spectrum

Spectroheliometric observations on the absorption spectrum of the Earth's atmosphere have been extended from 5μ to 21μ. The long wave limit of transmission imposed by the atmosphere occurs at 13.5μ. It is occasioned primarily by ν₂ of CO₂ and to a lesser extent by ν₂ of O₃. The carbon dioxide absorption blends with the pure rotation spectrum of water vapor at approximately 17μ to render the region beyond 13.5μ opaque to stellar radiation.