Chappuis bands

FIdthmann H, Beck C, Schinke R, Woywod C and Domcke W 1997 Photodissociation of ozone in the Chappuis band. II. Time-dependent wave packet calculations and interpretation of diffuse vibrational... 

A recent study of the vibrational-to-vibrational (V-V) energy transfer between highly-excited oxygen molecules and ozone combines laser-flash photolysis and chemical activation with detection by time-resolved LIF [ ]. Partial laser-flash photolysis at 532 mn of pure ozone in the Chappuis band produces translationally-... 

FIGURE 4.8 Absorption cross sections of O, in the Chappuis band at room temperature (adapted from Burkholder and Talukdar, 1994). 

The Huggins bands are in the 300- to 360-nrn region, whereas the 440- to 850-nrn region represents the Chappuis bands. As seen in Figs. 4.7 and 4.8, both absorptions are much weaker than the Hartley bands. 

The absorption in the ultraviolet and visible regions consists of the Hartley bands (2000 to 3200 A), the Huggins bands (3000 to 3600 A), and the Chappuis bands (4400 to 8500 A). The absorption coefficients of these bands arc given in Figs. VI I2 andVI 12b. Figure VI 12c shows the absorption coefficients in the vacuum ultraviolet region. 

Since the absorption spectra are diffuse over the entire spectral region, no assignments of transitions have been made from the analyses of the spectra. Hay and Goddard (449) have recently assigned the Hartley bands to a transition (origin at 3515 A) and the Chappuis bands to... 

At wavelengths greater than 310 nm, the Huggins bands correspond to the limit of the O3 ultraviolet absorption, and in the visible region (410— 850 nm) the Chappuis bands play an important role leading to the 03 photodissociation in the lower part of the atmosphere, troposphere, and lower stratosphere. 

Because of absorption in the three spectral ranges covered by the Hartley, Huggins, and Chappuis bands, the rate of photodissociation of 03 is a frequency of 10 2 sec-1 in the mesosphere, and greater than 10-4 sec-1 in the stratosphere and troposphere. 

Angione R.J. Medeiros E.J.jand Roosen R.G. (1976). Stratospheric ozone as viewed from the Chappuis band. Nature, 261, 289-290. 

Incidentally we note that Levene, Nieh, and Valentini (1987) measured vibrational state distributions for O2 following the photodissociation of O3 in the Chappuis band which qualitatively resemble those shown in Figure 9.11 for H2S. In order to interpret their results the authors surmised a model PES that actually has the same overall topology in the saddle point region as the one calculated for H2S. 

Fig. VI-12, (a)Absorption coefficients of (), Huggins bands (3000 to 3600 A) and Chappuis bands (44(H) to 8500 A) k (atm" 1 cm" ), 0 C, base 10. From Griggs (425), reprinted with permission. Copyright 1968 by the American Institute of Physics. (h) Absorption coefficients of O, Hartley bands (2000 to 3000 A), k is in units of atm" 1 cm"1, 0 C, base 10. From Griggs (425), reprinted by permission. Copyright 1968 by the American Institute of Physics, (c) Absorption coefficients of O, in the region 1000 to 2200 A. k is in units of (atm"1 cm" ), 0°C, base e. From Tanaka et al. (961), reprinted by permission. Copyright 1953 by the American Institute of Physics.

The Ta <— So transition moments to particular spin sublevels for the three lowest triplet states of the ozone molecule, 3B2,3 A2 and 3B, were calculated by the MCQR method in ref. [70] using CASSCF wave functions. Table 7 recapitulates results for electric dipole radiative activity of different S-T transitions in ozone [70]. The type of information gained form this kind of spin-orbit response calculations are viz. transition electric dipole moments and oscillator strengths for each spin sublevel T , their polarization directions (7), radiative lifetimes (r ) and excitation energies (En). The most prominent features of the Chappuis band are reproduced in calculations, which simulate the photodynamics of ozone visible absorption [78, 79]. Because the CM (M2) state cannot be responsible for the Wulf bands, the only other candidates ought to... 

As far as the attenuation of solar radiation is concerned, absorption by N02 and S02 is not significant in the troposphere, because of their very small number densities. The very weak absorption by in the Chappuis bands is also insignificant. 

The major sources of 0( P) are ozone photolysis in the Hartley continuum and Chappuis bands,... 

However, the total quantum efficiency for O3 destruction following photolysis is not observed to depend upon the wavelength of actinic radiation in this region (Castellano and Schumacher, 1962). Rather, the value of O-Og is measured as 2 both above and below the 611 nm threshold. In addition, lovely observations of the O2 product of O3 photolysis in the Chappuis bands using Coherent Anti-Stokes Raman Spectroscopy (CARS) have confirmed (Valentini, 1983) that it is only 02(X S g) which is formed in... 

It is convenient to discuss three regions of the absorption spectrum, separately the Hartley band from 2000 to 3000 A., the Huggins band from 3000 to 3500 A., and the Chappuis band from 4000 to 7500 A. The results of the ozone absorption coefficients measurements are displayed in Figures 2, 3, and 4, respectively. The absorption coefficients measured by the authors are tabulated in Table I. 

Figure 4. Absorption coefficients of ozone in region of Chappuis band, 4000 to 7500 A.

Woywod C., Stengle, M., Domcke, W., Flothmann, H. and Schinke, R. (1997) Photodissociation of ozone in the Chappuis band. I. Electronic structure calculations, J. Chem. Phys. 107, 7282-7295. 

Ozone has three major absorption bands for solar radiation named the Hartley, Huggins and Chappuis bands. It also has an absorption band at terrestrial infrared wavelengths (not relevant here). The strongest ozone absorption is in the... 

Ozone absorbs in the band of0.200-0.320 /zm (Hartley band) of the U V part of the spectrum and also in the visible range between 0.450 /zm and 0.700 /zm wavelengths (Chappuis band). A smaller absorption band can be identified in the infrared part of the spectrum. The strongest absorption is measured in the Hartley band. 

According to the above concept of ozone destruction, the troposphere is an inert medium concerning ozone chemistry. However, as Crutzen (1974) pointed out, there are several possible reaction steps for tropospheric 03. Thus ozone can be removed chemically from the air by transformation processes tabulated in Table 10. One reaction chain starts with the photolysis of 03, which is caused by radiations in the Hartley and Chappuis bands. The excited oxygen atoms, formed by Rl, are partly transformed to ground state atomic oxygen by R4. However, they also react with water vapour to give OH radicals (R5). The sum of reactions 1-5 can be written in the following way ... 

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