The Sun as Radiation Source

The sun is an intense source of corpuscular and electromagnetic radiation. The latter is called solar radiation. The sun is a spherical UV/VIS source with an average radius tgun of 6.9585 x 10 m, an average Earth-sun distance dg.g of 1.4957x10 m and a radiant power Pgu of 3.842x10 W. Therefore, the radiant exitance M of the sun calculates to Bolton, 1999). 

The distribution of global radiation depends strongly on atmospheric conditions, e. g. on the attenuation by clouds and fog, etc. Average values can be calcu- 

Altena FW, van Overveld JBJ, Giller H (2001) Technological Advances in Disinfection Lamps Leading to More Compact UV Sources, Conference Proceedings of the First International Congress on Ultraviolet Technologies, International Ultraviolet Assoc. (lUVA), June 14-16, Washington, DC, electronic release. 

Ametepe JD, Diggs J, Manos DM, Kelley MJ (1999) Characterization and Modeling of a Microwave Driven Xenon Excimer Lamp,/. Appl. Phys. 85, No. 11 7505-7510. 

Baum G, Oppenlander T (1995) Vacuum-UV-Oxidation of Chloroorganic Compounds in an Excimer Flow Through Photoreactor, Che.mosphe.re. 30, No. 9 1781-1790. 

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Since the discovery of the photoacoustic (PA) effect by Bell in 1880, who used the Sun as radiation source, a foot-operated chopper for modulation and an earphone as acoustic detector, the PA effect has found numerous applications as a sensitive and rather simple technique for determining optical, thermal and mechanical properties of all kinds of samples. This article focuses on methods and instrumentation employed in spectroscopic applications. Since photothermal (PT) spectroscopy is discussed elsewhere in the encyclopedia, PT schemes are only briefly mentioned here, whereas emphasis is put on instrumentation used in photoacoustic spectroscopy. 

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