Absorption Cross Sections of O2 and CO2 Continua in the Schumann and Far-uv Regions

Abstract

By means of a photoelectrical technique used in conjunction with a 3-m vacuum monochromator, the absorption cross section of the O2 continuum in the region 2350–1814 Å and the absorption cross section of CO2 in the region 2160–1718 Å have been measured. The cross section of the O2 continuum is 3.8 × 10−24 cm2 at 2350 Å; it slowly increases towards shorter wavelengths and reaches 10.7 × 10−24 cm2 at about 1980 Å, then increases very rapidly and reaches 7.1 × 10−22 cm2 at about 1814 Å. In the case of CO2, numerous discrete bands were found overlapping a weak continuum in the wavelength region below 1980 Å. The absorption cross section of the CO2 continuum is about 2 × 10−24 cm2 at 2100 Å; it gradually increases toward the shorter wavelength side, and reaches about 4 × 10−24 cm2 at 2000 Å. The continuum rises rapidly at 2000 Å and its value is 1.19 × 10−20 cm2 at 1718 Å. Origins of the continua of both O2 and CO2 are briefly discussed.