Ultraviolet radiation, depth dependence

J.M. Shick, M.P. Lesser, W.C. Dunlap, W.R. Stochaj, B.E. Chalker, J. Wu Won (1995). Depth-dependent responses to solar ultraviolet radiation and oxidative stress in the zooxanthellate coral Acropora microphthalma. Mar. Biol, 122,41-51. 

M.P. Lesser (2000). Depth-dependent photoacclimatization to solar ultraviolet radiation in the Caribbean coral Montastraea faveolata. Mar. Ecol. Prog. Ser., 192, 137-151. 

XPS spectra were recorded using unmonochromatized Mg K radiation (1253.6 eV), and an unmonochromatized He-resonance lamp was used for ultraviolet photoelectron spectroscopy (UPS). XPS spectra were taken with an analyzer resolution of 0.2 eV, and the net resolution measured as the full width at half-maximum (FWHM) of Au 4f(7/2) was 0.9 eV. The spectrometer is of our own construction and is, e.g., designed to provide optimum angle-dependent XPS or XPS(0) (12,l4). For high 5-values, the photoelectrons leave the sample surface near the grazing angel, and due to the limited escape depth of the electrons, this is a "surface sensitive" mode. In the "bulk sensitive" mode, for low 0-values, the photoelectrons exit near the surface normal, and hence more information from the "bulk" of the sample is obtained (15). 

The intensity of the interstellar radiation field—and consequently the photodissodation rates—decreases with depth into an interstellar cloud due to several factors. First, the grains present in the cloud will scatter and absorb the photons with a cross section that varies almost inversely with wavelength. The amount of continuum attenuation at each depth into the cloud depends on the extinction, the albedo and the scattering phase function of the grains (Sandell and Mattila 1975 Roberge, Dalgarno and Flannery 1981), only the first of which is sometimes known accurately at ultraviolet wavelengths. Cur-... 

Principally, three types of radiation are adequate for the sterilization of materials ultraviolet and gamma radiation. In the case of the radiation treatment of materials with ionizing (mostly gamma) radiation, a high exposure dose is necessary. Often a cobalt bomb (radioactive Co) is used for this purpose. The efficiency depends on the penetration depth. This procedure is adequate for the sterilization of plastics and other sensitive materials (e.g., for surgical purposes), as well as for foodstuffs (in Germany, only for spices). Metals or mineral materials only become germfree on the surface. 

The absorption of laser radiation in polymers is governed by Beer s law and the etch depth exhibits a logarithmic dependence on the incident laser fluence above a threshold value [137, 304, 611]. The penetration depth of ultraviolet laser radiation is usually greater than the etch depth, so that the surface left behind after ablation has been exposed to laser radiation [1229]. 

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