Oxygen Schumann-Runge bands

B. Atomspheric photochemistry. The photodissociation of oxygen in sunlight is the major photochemical process occurring in earth s atmosphere. The first intense allowed transition in O., is B - X 32 which occurs at 202.6 nm and is called the Schumann-Runge band system (Section 2.8). It merges intoa continuum beyond 175.9 nm and correlates with one oxygen atom 0(23P) in the ground state and one in the excited state O (2 D)... 

Fig. 2. Absorption spectrum of oxygen in the Schumann-Runge band system. The absorption coefficient, k, is defined by the equation I = la exp ( — kx), where h and I are the incident and transmitted light intensities and x is the layer thickness of the absorbing gas reduced to STP. This figure is taken from ref. (101) with the permission of The Journal of Chemical Physics.

The most recent measurements of the absorption coefficients of oxygen have been made by Watanabe et al. (101). For the transition 32u- -32 absorption intensities in the Schumann-Runge bands are shown in Figure 2 and in the Schumann-Runge continuum in Figure 3. 

Allen, M., and J.E. Frederick, Effective photodissociation cross sections for molecular oxygen and nitric oxide in the Schumann-Runge Bands. J Atmos Sci 39, 2066, 1982. 

Fang, T.M., S.C. Wofsy, and A. Dalgarno, Capacity distribution functions and absorption in Schumann-Runge bands of molecular oxygen. Planet Space Sci 22, 413, 1974. 

Kockarts, G., Absorption and photodissociation in the Schumann-Runge bands of molecular oxygen in the terrestrial atmosphere. Planet Space Set 21, 589, 1976. 

Lewis, B.R., S.T. Gibson, and P.M. Dooley, Fine structure dependence of predissociation linewidth in the Schumann-Runge bands of molecular oxygen. J Chem Phys 100, 6993, 1994. 

Nicolet, M., and R. Kennes, Aeronomic problems of molecular oxygen photodissociar tion, IV. Photodissociation frequency and transmittance in the spectral range of the Schumann-Runge bands. Planet Space Sci 37, 459, 1989. 

Fig. 3. Ultraviolet absorption spectra of high-density polyethylene film (0.20 mm) a polyethylene film in the quartz optical cell b only the optical cell. Solid and dotted curves show the absorption spectra observed when nitrogen or oxygen gas respectively was introduced (1 atm) in the 1 cm2 cell. Vibrational structures observed near 190 mp seem to be due to a part of Schumann-Runge bands of gaseous oxygen molecules in the optical cell. [Polymer J. 2, 606 (1971), Fig. 1]...

Molecular oxygen 02 (3 g) absorbs UV radiation below 2000 A. Absorption in the Schumann—Runge band range (1759—1950 A) causes excitation to one of the vibrational levels of the 02(3 ,p state. Light absorbed within this range may produce the reactions... 

The chemical-activation step is between one and two orders of magnitude faster than the subsequent collisional deactivation of vibrationally excited O2 Finally, the population of individual vibrational levels v" of O2 is probed through LIF in the Schumann-Runge band (ii after exciting the oxygen... 

Figure 13.12 shows the UV absorption profile of typical gases found (O2, H2O) and formed (O3) in the ambient environment of exposure tools. The Schumann-Runge band (180-210-nm) and continuum (<180-nm) regions dominate the photochemistry of molecular oxygen around 193 nm (of ArF exciplex laser) and 157 nm (of F2 excimer laser), respectively. 

Cheung A S C, Yoshino K, Freeman D E, Friedman R S, Dalgarno A and Parkinson W H 1989 The Schumann-Runge absorption-bands of 0 0 in the wavelength region 175-205 nm and spectroscopic constants of isotopic oxygen molecules J. Mol. Speotroso. 134 362-89... 

The onset of the continuum of the Schumann-Runge absorption bands of 02 is at 1750.5 A. The lower electronic state of the transition is the ground state and dissociates to ground-state oxygen atoms the excited... 

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