Ozone Absorption Cross Section Research Articles

O2 absorption cross sections (187–225 nm) from stratospheric solar flux measurements

The absorption cross sections of molecular oxygen are calculated in the wavelength range from 187 to 230 nm from solar flux measurements obtained within the stratosphere. Within the Herzberg continuum wavelength region the molecular oxygen cross sections are found to be about 30% smaller than the laboratory results of Shardanand and Rao (1977) from 200 to 210 nm and about 50% smaller than those of Hasson and Nicholls (1971). At wavelengths longer than 210 nm the cross sections agree with those of Shardanand and Rao. The effective absorption cross sections of O2 in the Schumann‐Runge band region from 187 to 200 nm are calculated and compared to the empirical fit given by Allen and Frederick (1982). The calculated cross sections indicate that the transmissivity of the atmosphere may be underestimated by the use of the Allen and Frederick cross sections between 195 and 200 nm. The ozone column content between 30 and 40 km and the relative ozone cross sections are determined from the same solar flux data set. The calculated ozone absorption cross sections agree with those of Inn and Tanaka (1959) and Bass and Paur (1981) to within 3%.

The direct and scattered solar flux within the stratosphere

Solar ultraviolet flux data were obtained within the atmosphere by using Fastie‐Ebert double monochromators carried on a balloon‐borne gondola and a rocket payload. Both the direct and scattered components of the solar ultraviolet flux at wavelengths from 190 to 320 nm were measured at the balloon float altitude of 40 km. The nearly identical spectrometer carried on the rocket flight measured the direct solar flux from 60 to 38 km during a parachute descent. The ozone column content above 40 km and the temperature profile and ozone density below 40 km are deduced from the scattered and direct solar flux components. It is shown that the Nimbus 7 solar flux data is consistent with the present data and with the ozone absorption cross sections of Inn and Tanaka (1959). The same is not true with the solar flux data of Broadfoot (1972), where a systematic error is clearly evident. The calculated and measured values of the scattered solar flux are found to agree quite closely. The scattered flux at 40 km is shown to be 20% of the direct flux at wavelengths longer than 300 nm and about 10% within the Schumann‐Runge band region of O2. This implies increased rates of photolysis for the production of O(1D), O(3P), and other minor species throughout most of the stratosphere and mesosphere. The 10% scattering within the O2 Schumann‐Runge band region leads to a 2% increase in O3 density at 40 km.

Relative O(1D) Quantum Yields in the near UV Photolysis of Ozone at 298 K

Abstract Mixtures of O3 with excess N2O were photolysed in the wavelength region 290 - 335 nm using monochromatic light with a band width of 4 nm. The resulting primary product atomic singlet oxygen, O(1D), in reacting with N2O produces in part NO which subsequently reacts with O3 giving rise to a weak infrared chemiluminescence. The emission was monitored with a cooled photomultiplier. The emission intensity is directly proportional to the rate of O(1D) production and it has been utilised to derive the relative O(1D) quantum yield as a function of wavelength between 295 and 320 nm. The data were normalised to a quantum yield of unity of 300 nm and corrections were applied to reduce the error resulting from the spectral band width of photolysing radiation. The O(1D) quantum yields show a temperature dependence. At 298 K the quantum yield is unity up to 305 nm, then declines to zero at 319 nm. At the dissociation limit, taken to occur at γ = 310.3 nm, the quantum yields is 0.57, i. e. considerably below unity. The implications of this result as well as the tail toward longer wavelengths and the temperature dependence are discussed. Ozone absorption cross sections are also reported.

Detection Method of Ozone in Atmosphere Using Differential Absorption Technique with CO2 Laser

The measurement of the absorption lines of ozone using the emission lines of the (00°1–02°0) band of CO2 laser was discussed. As the result of experiment, it was made obvious that the absorption cross section of ozone pressurized up to 760 Torr was (2.4±0.08)×10-19 cm2 at the frequency of 1052.1956 cm-1 corresponding to the P(14) laser line of the (00°1–02°0) band. By the use of this value, the minimum detectable concentration of ozone was estimated for the long path absorption. Accordingly, it was concluded that the concentration of 0.1 ppm in ambient atmosphere would be able to be detected by using the laser power of only 0.3 µW for the path length of 500 m.