Schumann-Runge continuum

The mechanism for the photochemical formation of ozone in the Schu-mann-Runge continuum appears to be quite simple. It has been studied 

There is no evidence that XD atoms react differently from 3P atoms. Quantum yields of less than 2 may be accounted for by the reaction 

---

FIGURE 4.2 Absorption coefficients for 02 in the Schumann-Runge continuum. Note log scale. (Adapted from Inn, 1955.)... 

Fig. V-12. Absorption coefficients of O, in the region 1100 to 2000 A. k is in units of atm em 0°C, base e. 1300 to 1700 A, Schumann-Runge continuum. 1750 to 1950 A, Schumann-Runge bands. From Watanabe c al. (1014), reprinted by permission. Copyright 1953 by the American Institute of Physics.

A small amount of 0( >) is produced from the r" = 1 and 2 levels by absorption of the solar radiation below 1850 A of the Schumann-Runge continuum (40) contributing to Of1D) atoms in the mesosphere and stratosphere. 

O2(h X + ) in the Upper Atmosphere. The atmospheric band of O, observed in the upper atmosphere (40 to 130 km) indicates that the 02( ) is produced by photochemical processes (1000). The most likely process is the photolysis of 02 in the Schumann-Runge continuum followed by the energy transfer reaction (350)... 

Schumann-Runge Continuum (adiabatic curve following one 0(3P2) atom, one O( D) atom)... 

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. 

Fig. 3. Absorption spectrum of oxygen in the Schumann-Runge continuum. This figure is taken from ref. (101) with the permission of The Journal of Chemical Physics.

Very weak absorption bands in the region 2500 to 3000 A correspond to the forbidden transition /1,ZU+-X 3Z9" (see selection rules 1-10.2). The band system is called the Herzberg 1 band. Second absorption bands in the region 1750 to 2000 A correspond to the B3Z -X3 transition and are called the Schumann-Rungc system. The region 1300 to 1750 A is continuous and is called the Schumann-Runge continuum. Below 1300 A numerous Rydberg transitions have been observed [Yoshino and Tanaka (1066)]. 

The f1/)) state of atomic oxygen yields the forbidden red-line radiations (6300 and 6364 A) that are prominent in the aurora and dayglow, twilight, and nightglow. In the dayglow, the major source of Of1D) is photodissociation in the Schumann-Runge continuum [180] ... 

Because of its strong absorption (a = 1.5 x 10 17cm2 at 140 nm), the Schumann-Runge continuum (130-183 nm see Figure 4.32, left panel) is only important in the thermosphere, and from the point of view of photolysis, plays a dominant role only above 90 km. Each photolysis event leads to the production of two oxygen atoms, one in the ground 3P state and the other in the excited 1D state. As shown by Hudson et al. (1966) and by Lean and Blake (1981), the temperature dependence... 

---