Deep ultraviolet radiation

Since the atmosphere shields us from most deep ultraviolet radiation and from infrared radiation, the bulk of visible light (the solar spectrum) ranges from 350 to 750 nm. The 25,000 Frauenhofer15 "dark" lines are interruptions (in the range 295 to 1000 nm) in the continuous solar emission spectrum, due to absorption by the chemical elements present in the sun s atmosphere. Ultraviolet radiation was discovered by Ritter16 in 1801. Some radio waves do penetrate the earth s atmosphere, and they are most intense during solar storms. Infrared radiation also penetrates to some extent. 

Acrylic is a generic name for derivatives of acrylic acid, of which methyl methacrylate is the most important. Polymerization is controlled to produce chain length of 800 to 3,000 monomer units. A small amount of plasticizer such as dibutyl phthalate may be added before bulk polymerization to assist in deep molding. The outstanding property of polymethyl metliacrylate is 0 transparency resistance to ultraviolet radiation from fluorescent lamps and ability to be... 

Films of polyphthalaldehyde, sensitized by cationic photoinitiators, have been imaged at 2-5-mJ/cm in the deep ultraviolet (DUV) (see Section 3.10), at 1 pC/cm (20 kV) electron beam radiation and at an unspecified dose of Al-A x-ray radiation. The ultimate utility of this "self-developing" resist system will depend upon its efficacy as an etch barrier. It seems clear that such materials would not serve as adequate etch masks for... 

In the case of marine deposition, the transport of particles through the air results in the anneahng by ultraviolet radiation from the Sun. The reset minerals then act as accumulators of lattice damage once they are buried. The technique has been estabhshed for wind-blown deposits such as dunes and loess deposits. Wintle and Huntley (1979) apphed it to deep-sea sediments, building on initial studies by Huntley and Johnson (1976). Subsequently, there has not been a great deal of work on deep-sea sediments, and most of the interest has shifted to sand dunes and loess deposits where the method provides a unique dating tool. 

However, some scientists believe that the young Earth was too inhospitable a place for life to have developed on its surface at all lacking O2, the atmosphere would also have lacked its present-day stratospheric layer of ozone (O3), which screens large quantities of harmful ultraviolet radiation from the surface. They believe that a more likely environment for abiogenesis (life from prelife) was in the vicinity of deep-sea vents, holes in the crust under the ocean from which hot, mineral-laden water flows. 

A photomask is a nearly optically flat glass (transparent to near UV) or quartz plate (transparent to deep UV) with a metal absorber pattern printed on one side. The metal pattern is typically a 0.1 /zm thick chromium layer. The metal absorber pattern on a photomask is opaque to ultraviolet radiation, whereas glass... 

Many polymers are altered on exposure to ultraviolet radiation, and this has led to the development of photolithographic techniques using conventional UV radiation from a merciny vapor lamp with an emission spectrum of A, = 430 nm, 405 nm, and 365 nm. When resolution of features of less than 2 pm is required, then deep UV soinces with A 150 to 250 nm may be used, provided resists that absorb in this wavelength region can be selected. 

Laser radiation can be produced in different operating modes (continuous, pulsed) and in different media (solid state, gas, dye). Pulse durations range from milliseconds to femtoseconds, as in nanosecond pulsed exdmer gas lasers which radiate in the deep ultraviolet (UV) (wavelength 157 to 351 nm) and femtosecond or millisecond pulsed solid state lasers (266 to 1070 nm). Continuous wave (cw) operation CO2 gas lasers radiate in the IR (10.6 pm). 

Ultraviolet radiation in industry may be found aronnd electrical arcs, and such arcs should be shielded by materials opaque to the ultraviolet The fact that a material may be opaque to ultraviolet has no relation to its opacity to other parts of the spectrum. Ordinary window glass, for instance, is almost completely opaque to the ultraviolet in snnlight at the same time, it is transparent to the visible light waves. A piece of plastic, dyed a deep red-violet, may be almost entirely opaque in the visible part of the spectrum and transparent in the near-nltraviolet. Electric welding arcs and... 

Deep ultraviolet (DUV) Short-wavelength ultraviolet radiation. 

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