Atmospheric Radiation and Photochemistry

In this chapter, we give a brief overview of the fundamentals of spectroscopy and photochemistry needed in atmospheric chemistry for detailed treatments, see Calvert and Pitts (1966), Okabe (1978), Turro (1978), Wayne (1988), and Gilbert and Baggott (1991). Specifics for individual molecules are found in Chapter 4. Excellent treatments of atmospheric radiation are given by Liou (1980), Goody and Yung (1989), and Lenoble (1993). 

In the five years since the first volume was published, there has been increased interest in the chemistry within gas lasers and the chemistry induced by laser radiation, the kinetics and photochemistry within fusion and industrial plasmas, as well as in the normal and perturbed lower and upper atmosphere. And. since the Three Mile Island accident there has been renewed interest in radiation damage to living and nonliving things. This state of affairs has not only precipitated a variety of spectroscopic studies, but has also brought more attention to the nonspectroscopic aspects of excited state production and the interaction of excited species. The latter topic was stressed in the earlier volume and the emphasis is retained here. 

In Chapter 3 we examined the interaction of incoming solar radiation in the UV and visible regions of the spectrum with atmospheric gases, which drives atmospheric photochemistry. This incoming solar radiation... 

Historically, the photochemistry of oxygen and ozone has been of considerable interest because of the importance of oxygen and ozone in the atmosphere. In 1881 Hartley (39) postulated that ozone was a normal constituent of the upper atmosphere and that absorption of solar radiation by ozone could account for the limitation of the solar spectrum at about 3000 A. These speculations were not definitely corroborated until 1913 by Fabry and Buisson (26). The formation of ozone from oxygen in ultraviolet light in the region 1400-1900 A. was first reported by Lenard (53) in 1900 and afterwards confirmed by Goldstein (34) in 1903. 

Photodissociation is at the heart of photochemistry (Turro 1965, 1978 Calvert and Pitts 1966 Ben-Shaul, Haas, Kompa, and Levine 1981 von Btinau and Wolff 1987 Wayne 1988 Klessinger and Michl 1989). In many cases, the photofragments are radicals which rapidly undergo secondary and tertiary reactions. Photodissociation is the motor for many important chain reactions determining the complex chemistry in the atmosphere. The sun supplies sufficient UV radiation to keep the motor going (Okabe 1978). The ozone cycle,... 

---