Far-ultraviolet light

Perfluoroacetal or perfluoroketal polymethacrylates containing norbornene substituents and having improved transparency were prepared and were suitable for use in photolithography with far-ultraviolet light at a wavelength of 180 nm or shorter. These materials are particularly useful in the formation of a fine resist patterns. 

O2 is ionized by far ultraviolet light, while the ionization of Nj requires s< ar X rays. That the ionization energy of Nj is greater than... 

Tuveson, R.W., M.R. Berenbaum, and E.E. Heininger Inactivation and Mutagenesis by Phototoxins using Escherichia coli Strains Differing in Sensitivity to Near and Far-Ultraviolet Light. J. Chem. Ecol. 12, 933 (1986). 

Detection of this particle accumulation has so far been done visually. To make the particles more easily visible, they have been chemically treated in order to make them light up or flouresce when struck by an ultraviolet light. The operator sits in a darkened room in which the test pieces are illuminated by ultraviolet light. Cracks show up very clearly and in principle this method of inspection is acceptable. Despite the effiency of this method it is well known that a large number of defective pieces pass this test. Why is it so ... 

Skin lighteners, freckle and age spot removers, and other remedies for hyperpigmentation are not actually bleaches like the products listed so far. The active ingredient is hydroquinone, which inhibits melanin formation when applied to the skin. Since the effect is easily reversed by exposure to sunlight or ultraviolet light, a sunscreen is usually included in the formula. 

Direct photochemical reactions in the stratosphere induced by far ultraviolet solar light are well known to be important for the chemistry of the atmosphere. However, only a small fraction of the solar energy flux is in this spectral region. 

Fig. 1. Ultraviolet light curves of beta Lyrae observed with the 0A0-2 (Kondo, McCluskey and Eaton 1976, An. Space Sci. , 41. 121). Note the deepening of the secondary minimum in the far-ultraviolet.

All prebiotic polymerization reactions, which are dehydration reactions, are thermodynamically unfavorable. This free energy barrier can be overcome in two ways. The first is to drive the dehydration reaction by coupling it to the hydration of a high energy compound, and the second method is to remove the water by heating. In principle, visible or ultraviolet light could drive these reactions, but so far no one has demonstrated adequately such processes. 

Light absorption by oxygen has been observed from the near infrared to the far ultraviolet. Absorption above about 2500 A. is of some interest in connection with proposed photochemical reactions of oxygen with some other molecules. For the formation of ozone, however, the middle and short ultraviolet region is of primary interest. 

The relation between the excitation state of the surface bonds and the activation energy, discussed so far, is easy to understand when the rate-determining step of the reaction considered involves the dissociation of the more or less excited surface bond. In order to investigate the importance of the excitation state of the surface bond in a reaction without oxygen transition, the decomposition of isopropyl alcohol vapour on a ZnO catalyst in the dark and in ultraviolet light has been studied 93-95). 

The visible spectrum extends approximately from 4,000 to 8,000 A. The human eye is not sensitive to light of wave lengths much shorter or longer than these. The near infrared region extends from 8,000 up to perhaps 200,000 A, and the far infared region extends still further toward the long waves from meters to thousands of meters, which are familiar to anyone who turns a radio dial. On the shorter side of the visible spectrum, we have ultraviolet light... 

All wave lengths shorter than the threshold of Eq. (3.2) can eject photoelectrons. Thus a metal with a small work function of two volts (which certain alkali metals have) has a threshold in the red and will react photoelectrically to visible light, while a metal with a work function of six volts would have a threshold about 2000 A, and would be sensitive only in the rather far ultraviolet. Most real metals lie between these limits. 

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