Schumann-Runge system

The X3 -—> B3X- transition is allowed and as seen in Figs. 4.2 and 4.3 results in an absorption in the 130-to 200-nrn region known as the Schumann-Runge system. The banded structure from about 175 to 200 nm corresponds to transitions from v" = 0 as well as v" = 1 (i.e., hot bands) of the ground X3S state to different vibrational levels of the upper state. 

FIGURE 4-1 Potential energy curves for ground and first four excited states of 02. S-R = Schumann-Runge system, H = Herzberg continuum, A-A = atmospheric bands (adapted from Gay-don, 1968). 

The Schumann-Runge bands converge to the limit at 1750 A corresponding to the production of Of3/3) + Of1/)). The integrated absorption coefficients of the Schumann-Runge system from (0,0) to (20,0) have been... 

Ackerman and Biaume (37) have observed that rotational lines become diffuse at if = 4, 8, and 11 for the Schumann-Runge system. They attribute the difluseness to predissociation. 

The photochemical evidence for predissociation obtained in this work and in other studies has been discussed by Volman (94), and will be referred to in later sections. The evidence thus far obtained strongly reinforces the suggestion of Flory (28) that predissociation is possible following absorption in the discrete portion of the Schumann-Runge system. 

Either of these processes, however, appears to be unlikely, and the first has been rejected by Benson (13). Although radiation from the 32u state is possible, it is precisely the vibrationally excited states of 32 which are known not to radiate. Emission bands in the Schumann-Runge system for v > 2 have not been found (21,94,105), and the evidence is now strong that predissociation from v 3 accounts for the absence of these emission bands. Therefore, it is most probable that reac-... 

Figure 4-44- Detailed structure of the (5-0) band of the Schumann-Runge system of 62 in the spectral range of the 5 (0-0) band of nitric oxide. From Cieslik and Nicolet (1973).

Murtagh, D.P., The O2 Schumann-Runge system New calculations of photodissociation cross sections. Planet Space Sci 36, 819, 1988. 

Emission bands of the Schumann-Runge system have also been observed. These are due to transitions from various vibrational levels of the Si state to various vibrational levels of the S state the highest vibrational level of the S state thus detected is at a height 27 840 cm above the ground vibrational state. 

The photolysis of O2 at the Schumann-Runge system is an important chemical process to form the ozone layer in the stratosphere. The chemistry of the stratosphere will be discussed in Chap. 8. The absorption spectmm of O3 formed there plays an important role to determine the vertical distribution of the solar spectrum at different altimde and also the shorter wavelength edge in the troposphere. 

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