Radiation Wavelength

In FT-Raman spectroscopy the radiation emerging from the sample contains not only the Raman scattering but also the extremely intense laser radiation used to produce it. If this were allowed to contribute to the interferogram, before Fourier transformation, the corresponding cosine wave would overwhelm those due to the Raman scattering. To avoid this, a sharp cut-off (interference) filter is inserted after the sample cell to remove 1064 nm (and lower wavelength) radiation. 

Shorter-wavelength radiation promotes transitions between electronic orbitals in atoms and molecules. Valence electrons are excited in the near-uv or visible. At higher energies, in the vacuum uv (vuv), inner-shell transitions begin to occur. Both regions are important to laboratory spectroscopy, but strong absorption by make the vuv unsuitable for atmospheric monitoring. Electronic transitions in molecules are accompanied by stmcture... 

These restrictions do not apply to the less intense fluorescent tubes installed in the UVIS or MinUVIS (Fig. 6) or Universal UV lamps (Fig. 7). Black glass surrounds or screens serve as filters. Unfortunately account is often not taken of the fact that the transparency for short-wavelength UV light decreases appreciably with increasing duration of irradiation (Fig. 8). So it is advisable to change the filters of lamps intended for short-wavelength radiation at regular intervals. They can... 

The same UV lamps discussed in Section 2.2.3.1 are employed to excite fluorescence. Excitation is usually performed using long-wavelength radiation (2 = 365 nm), shorter wavelengths are occasionally employed (e.g. 2 = 302 nm, DNA analysis). 

One of the most direct methods is photoelectron spectroscopy (PES), an adaptation of the photoelectric effect (Section 1.2). A photoelectron spectrometer (see illustration below) contains a source of high-frequency, short-wavelength radiation. Ultraviolet radiation is used most often for molecules, but x-rays are used to explore orbitals buried deeply inside solids. Photons in both frequency ranges have so much energy that they can eject electrons from the molecular orbitals they occupy. 

The wavelength is rather long— 3.40 m—but radio waves are known as long wavelength radiation. See Figure TA for a sense of the wavelengths of electromagnetic radiation. 

The short-wavelength radiation necessary for this decomposition is absent in the lower layers of the atmosphere it is likely that the photolysis of ethyne occurs via C-H cleavage to give radicals, which react with methane to give methyl radicals, the recombination of which affords ethane ... 

This quantity is the total amount of radiation at all wavelengths radiating through the surface of the sphere and is simply the Stefan-Boltzmann Law multiplied by the surface area of the photosphere. 

Life on Earth requires the energy from the Sun as a primary energy source but it must be protected from all of the radiation at shorter wavelengths. Radiation shorter than 323 nm can break the C-C bond and this would lead to mutations or complete photolytic destruction of carbon-based life forms. The protection from the short-wavelength radiation is achieved on Earth in two ways the ozone layer and the photic zone. 

Both processes are switched on by the absorption of short-wavelength radiation X < 240 nm for H20 and X < 230 nm for C02. On the assumption that H atoms escape from the atmosphere, there is a net gain in oxygen to the atmosphere. Reactions of O atoms and 02 chemistry would then lead to the formation of a small ozone layer with a low ozone concentration. 

Greenhouse effect Atmospheric gases trap long-wavelength radiation emitted by a planet, resulting in an increased surface temperature. 

Short-wavelength shield The protection of the surface of a planet from dangerous short-wavelength radiation from the local star. On the Earth, the ozone layer shields the surface, as does the photic zone. 

The reverse process may be possible, using short-wavelength radiation in a region where the cyclobutene absorbs strongly ... 

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