Chappuis Band Research Articles

Solar UV radiation and its absorption in the mesosphere and stratosphere

Solar radiation of λ>175 nm and of Lyman-alpha at 121.6 nm is absorbed in the mesosphere and stratosphere by molecular oxygen (λ 200 nm. This paper describes the photodissociation processes resulting from absorption in the Schumann-Runge bands and Herzberg continuum of molecular oxygen and also in the Hartley, Huggins and Chappuis bands of ozone. Special consideration is given to differences between the stratospheric and mesospheric problems.

Atmospheric Ozone: Determination by Chappuis-Band Absorption

Abstract Ozone content in the atmospheric column above Mauna Loa Observatory, Hawaii, was determined in experiments by measuring the attenuation of sunlight in the visible spectrum Chappuis bands (500 nm<λ<700 nm wavelength). The dominant source of uncertainty in such determinations is the accuracy with which the magnitude of the published Chappuis-band absorption coefficients are known. Values of ozone (for 42 clear days) obtained by using Vigroux's absorption coefficients differed systematically, and were 17.6% smaller than those derived simultaneously in time and space with a Dobson spectrophotometer. The agreement with the Dobson values improves, but is not perfect, when Inn and Tanaka's absorption coefficients are used in the data analysis. Until more accurate information becomes available on ozone absorption coefficients, spectrophotometric-derived values of atmospheric ozone must be considered uncertain to 10–20%.

Photofragment spectroscopy of ozone in the uv region 270–310 nm and at 600 nm

Both O(3P) and O(1D) atom fragments are observed in the photofragment spectroscopy of O3 in the Hartley band absorption region 270–300 nm. The quantum yield for O(3P) is 0.1 at 274 nm. The dissociation partner for O(3P) is O2(X3Σ−g) and that for O(1D) is O2(a 1Δg). The O2(X 3Σ−g) fragment is populated in a range of vibrational levels, v?0−10. For the O2(a 1Δg) fragment, all energetically accessible vibrational levels are populated at each energy of bombardment. In the Chappuis bands at 600 nm the O2(X 3Σ−g) photofragment is produced principally with v=0, 1. Photofragment angular distributions are measured in the uv for both O atom dissociation products at each wavelength of bombardment. A theoretical angular distribution for O(1D) is derived and the resultant prediction is in good agreement with the experimental results.

Configuration interaction calculations for the ground and excited states of ozone and its positive ion: Energy locations and transition probabilities

Large-scale configuration interaction calculations (including energy extrapolation) are reported for the various states of ozone and its positive ion. The first four dipole-forbidden electronic transitions in the O 3 spectrum are calculated to occur at 1.20, 1.44, 1.59, and 1.72 eV, respectively, while the corresponding low-energy-allowed species known as the Chappuis, Huggins, and Hartley bands are predicted to possess vertical excitation energies of 1.95, 3.60, and 4.97 eV, respectively. These results all appear to fit in quite well with the observed location of the pertinent spectral features, with respect to both energy and intensity. The 5- to 8-eV region of the ozone spectrum is found to be characterized by a series of double-excitation transitions out of the highest three occupied orbitals to the lowest unoccupied 2b 1(π ∗) species. The strong features observed at 9.3 and 10.2 eV are thereupon calculated to result primarily from transitions into the 7a 1 (σ ∗) MO (calculated 9.29 and 10.05 eV) and in the former case also from the 3 s members of the various O 3 Rydberg series (calculated 9.21 and 9.38 eV). Finally the order of the first three ip's is found to be 6 a 1, 4 b 2, and 1 a 2, while the feature in the neighborhood of 16 eV is attributed to a shake-up state of 2 B 1 symmetry.

Stratospheric ozone as viewed from the Chappuis band

Stratospheric total ozone values have been obtained for the period 1912–50 from analysis of Smithsonian data. Naturally caused variations of 25% or more are common over time scales ranging from months to decades. We suggest that the ozone layer acts as a shutter on the incoming solar energy, providing one of the long sought trigger mechanisms betwen solar activity and climatic change. The present state of knowledge of ozone climatology is not sufficient to support popular speculations about man's effects on the ozone layer.

An Analytic Formula for Heating Due to Ozone Absorption

An attempt was made to devise a simple expression or formula to describe radiative heating in the atmosphere by ozone absorption. Such absorption occurs in the Hartley, Huggins, and Chappuis bands and is only slightly temperature and pressure dependent.

中間圏における負イオン粒子について

The polar cap absorption (PCA) especially in twilight condition is considered taking into account of negative ion O- which is possibly formed through the charge transfer process, O-2+O→O2+O-+1.2eV(6) and it follows the negative ion in the upper mesosphere is not O-2 but O- in general, [O-]/[O-2]_??_α6/d(O-)[O] where α6 be presumably 10-11 cm3 sec-1 or so. Then the screening effect of O3 Chappuis bands absorption becomes important.

Determination of the vertical distribution of ozone by satellite photometry

The Echo communications satellite (1960 Iota I) launched by the United States on August 12, 1960, is designed to be a good reflector of visible solar radiation. Under certain favorable orientations of its orbital plane, ground observers are able to watch it enter (and leave) the earth's shadow. Immediately before and after such observable eclipses, the satellite is illuminated by radiation that has been modified as a result of a long traverse in the earth's atmosphere. In wavelengths near 6000 A, the modification is one of attenuation (extinction) caused by two distinct physical processes: scattering by air molecules, and absorption by ozone present mainly in the lower stratosphere and possessing weak absorption bands (the Chappuis bands). If in this region of the solar spectrum we measure the differential attenuation between a pair of properly selected wavelengths, and are able to subtract out the contribution due to differential scattering, we can isolate the differential absorption due to ozone, and hence derive the average concentration of this constituent in the path of the solar ray instantaneously incident on the satellite. By making the measurements at successive instants, the altitude distribution of the ozone concentration can also be determined. Even though ozone concentration does not reach values higher than 10−6 of the air concentration at any altitude in the earth's atmosphere, the long ray paths involved in the satellite illumination make it possible to determine this concentration with sufficient accuracy. Alternatively, if the wavelengths selected are such that the differential ozone absorption is negligible, we have in principle a method of determining the air density at various heights from the differential scattering alone. In this paper we present the details of the theory, and report on some preliminary determinations of the ozone distribution obtained by monitoring the Echo satellite in two wavelength bands centered at 5900 and 5295 A respectively.

Explanation of the Brightness and Color of the Sky, Particularly the Twilight Sky

By use of the Rayleigh scattering theory for pure air, primary scattering and known upper air densities from rockets, the brightness of the zenith twilight sky was calculated and values were obtained two to four times greater than those observed at Sacramento Peak, New Mexico ( J. Opt. Soc. Am.42, 353 ( 1952). The attenuation of the atmosphere there was observed to be twenty percent above that of the Rayleigh theory, and the ozone thickness was measured to be about 2.2 mm. When the absorption of the Chappuis band of ozone in the visible spectrum was added to the Rayleigh theory, the calculated sky brightness came into agreement with observation for solar depression angles below the horizon from about 0° to 6°. For the sun below 7° the calculated zenith sky brightness fell rapidly below the observed brightness, showing that primary scattering in the atmosphere above about 60 km does not contribute appreciably to the brightness, as has long been known ( J. Opt. Soc. Am.28, 227, 1938).Calculation showed that during the day the clear sky is blue according to Rayleigh, and that ozone has little effect on the color of the daylight sky. But near sunset and throughout twilight ozone affects the sky color profoundly. For example, in the absence of ozone the zenith sky would be a grayish green-blue at sunset becoming yellowish in twilight, but with ozone the zenith sky is blue at sunset and throughout twilight (as is observed), the blue at sunset being due about 13 to Rayleigh and 23 to ozone, and during twilight wholly to ozone.

The effect of visible solar radiation on the calculated distribution of atmospheric ozone

In the last issue of this Journal the authors have described and given the results of a theoretical calculation of the distribution of atmospheric ozone1, considering the ozone to be maintained in a photochemical steady state by solar radiation that is absorbed by oxygen and ozone. The resulting distribution resembles rather closely the actual distribution so far as it is now known from observation, and suggests that the photochemical picture is adequate to account for the major aspects of atmospheric ozone. Certain factors not taken into account in the calculation, but which are of importance for the complete picture, were briefly discussed at the end of the above‐mentioned paper. Two of these were the influence of the absorption of ozone in the visible spectrum (the Chappuis bands) and the influence of air‐movements on the amount of ozone over any particular point on the Earth's surface. It is the purpose of this and another short article, which will follow to expand upon these two points.