Middle-ultraviolet

The development of oxygen in the early atmosphere led to a concomitant buildup in the ozone density and hence a significant decrease in middle ultraviolet radiation impinging upon the Earth s surface. As will be discussed in detail below, ozone arises following the photodissociation of O2 in the far ultraviolet below 242 nm. 

Until quite recently, direct measurements of o(>d2)(X) were limited by the very real experimental difficulties associated with the highly efficient deactivation of O ( D2) by O3, as well as the need to provide a sensitive probe for atomic oxygen atoms in the ground Pj state as well as in the electronically excited D2 state. The development of resonance spectroscopic techniques for time-resolved detection of O ( Pi) has permitted monitoring of this state at densities of ca. 10 cm with an instrumental bandwidth in excess of 10 MHz. When combined with the use of high intensity photolysis sources such as the excimer lasers and frequency quadrupled Nd/YAG, it has proved possible to measure directly the yield of 0( D2) and O( Pj) at several discrete wavelengths in the middle ultraviolet. 

A relatively simple spectroscopic model of O3 absorption in the middle ultraviolet has been proposed (Adler-Golden et al., 1982). This model assumes that the internal energy of an O3 molecule adds fully to that of the absorbed ultraviolet photon and that the quantum yield of O ( Eh) varies smoothly from zero at some threshold energy (calculated as being 32900 cm ) to unity 600 cm above this threshold. The model, which is quite successful in rationalizing the observed Hartley band spectrum for vibrationally excited O3, accurately reflects the experimental temperature dependence of the ( Dz) yield at 313 nm and also predicts a dependence of oCdj) ) upon wavelength in the region above 304 nm that is quite similar to that observed in a previous experimental study... 

Krasnopolsky, "V.A. Middle ultraviolet spectroscopy of Pluto and Charon. Icarus 2001, 153, 211-2 4. 

Chapman, J. and Hardy, J. T. (1988). Effects of middle ultraviolet radiation on marine fishes Final Report Oregon State University US EPA Coop. Argrmt. CR-812688-02-0. 

Feller, R. L., Curran, M., Colaluca, V., Bogaard, 1., et al. (2007). Photochemical deterioration of poly (vinylbutyral) in the range of wavelengths from middle ultraviolet to the visible. Polymer... 

Carbon dioxide is transparent in the visible and near-to-middle ultraviolet regions, at least down to 210 nm (Jiv <5.91 eV), both in the liquid phase [154] and in the gas phase [117]. 

Additions to the PLM include monochromatic filters or a monochromator to obtain dispersion data (eg, the variation in refractive index with wavelength). By the middle of the twentieth century, ultraviolet and infrared radiation were used to increase the identification parameters. In 1995 the FTIR microscope gives a view of the sample and an infrared absorption pattern on selected 100-p.m areas (about 2—5-ng samples) (37). 

Changes of fibre optical properties and thus changes of the analyte can be detected in the ultraviolet (UV), visible (VIS), near infrared (NIR) and middle/far infrared (IR) regions. There are only a few materials sufficiently transparent in the UV region, and among them, the pure silica is uniquely suitable for fibre drawing. From Figure 5 it can be seen that the UV... 

To visualize whether or not wood can be delignified by laccase III, ultraviolet photomicrographs (280nm) were taken before and after treatment of 0.5 mjLt cross-sections of red pine with laccase III (Figure 11). After enzyme treatment areas having an absorbance less than 0.2 in the secondary wall, and an absorbance less than 0.4 in the middle lamella, appeared. Each part of the secondary wall, middle lamella, and cell junction was subjected to ultraviolet microscopy, and absorption curves in the 240-300nm region were determined. The absorption curves of three samples after treatment... 

It is a remarkable fact that the contemporary history of absorption and emission spectroscopy began simultaneously, from the simultaneous discoveries that Bunsen and Kirchhoff made in the middle of the 19th century. They observed atomic emission and absorption lines whose wavelengths exactly coincided. Stokes and Kirchhoff applied this discovery to the explanation of the Fraunhofer spectra. Nearly at the same time approximately 150 years ago, Stokes explained the conversion of absorbed ultraviolet light into emitted blue light and introduced the term fluorescence. Apparently, the discovery of the Stokes shift marked the birth of luminescence as a science. 

The middle phase, which is characterized by a hyperchromic shift and the formation of acid-soluble oligonucleotides monoesterified phosphate can be detected. In this phase, the increase of ultraviolet absorption and of acid-soluble oligonucleotides is linear with the reciprocal... 

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. 

Figure 3. Ultraviolet Spectra of c-AMP (top curve), c-GMP (middle curve), and c-IMP (bottom curve).

Figure 3.3-8 Normalized detectivity D and equivalent number of light quanta for different detectors for optical radiation. FUV, UV, VIS, NIR, MIR, FIR far ultraviolet, ultraviolet, visible, near, middle, and far infrared region.

I. Isolated lignin preparations. Tappi 45 826-829 Boutelje JB, Eriksson 1 (1982) A UV-microscopy study of lignin in middle lamella fragments from fibers of mechanical pulp of spruce. Sven Papperstidn 85 R39-R42 Boutelje JB, Jonsson U (1980) Ultraviolet microscope photometry of pulp fibers. UV-absorbance and its relationship to chlorine number, kapp number and lignin content. Cellul Chem Technol 14 53-67... 

---