Vacuum-UV region

In the UV and vacuum UV regions, the efficiency of the biological effects is usually evaluated based on the incident photon. The efficiency is expressed in units of m, and is usually called the action cross section. Another definition used to evaluate the efficiency is based on the absorbed energy, and is expressed in Gy ( = kg/J). This is commonly used in radiobiology. In this chapter, the word efficiency is used based on the incident photon, except when particularly described, because the interactions of photons with molecules are neglected when discussed using Gy. 

A decrease in the biological efficiency was observed in the vacuum UV region because of the shielding effect of the outer materials in a spore. 

In the vapour phase photolysis of hydrocarbons in the vacuum UV region (120-200 nm), the main fragmentation process results in the elimination of hydrogen. 

A full response in the UV and vacuum UV is accessible only with detectors fitted with special fluoride windows. The cut-off wavelengths of optical glass (g) and of silica (q) are shown in Figure 7.25. For some special applications windowless detectors are used and the sensitivity is then greatly extended in the vacuum UV region and beyond. 

In the present paper, we show that it is possible to calculate both vibrational and electronic transitions of H2SO4 with an accuracy that is useful in atmospheric simulations. We calculate the absorption cross sections from the infrared to the vacuum UV region. In Section 2 we describe the vibrational local mode model used to calculate OH-stretching and SOH-bending vibrational transitions as well as their combinations and overtones [42-44]. This model provides frequencies and intensities of the dominant vibrational transitions from the infrared to the visible region. In Section 3 we present vertical excitation energies and oscillator strengths of the electronic transitions calculated with coupled cluster response theory. These coupled cluster calculations provide us with an accurate estimate of the lowest... 

Current instruments allow CD measurements not only to be performed in the vacuum-ultraviolet (vacuum-UV) region X < 190 nm), but also in the infrared (IR) spectral region. This means that not only chiral absorption effects related to excitations of molecular electronic subsystems are amenable to experimental observations, but also effects involving excitations of the nuclear subsystems of molecules ( vibrational circular dichroism VCD) Recently, results of VCD experiments with cyclopropanes were published. Therefore, in the present chapter the discussion of chiroptical properties of cyclopropanes can include vibrational circular dichroism. Hence, the discussions of chiroptical properties of cyclopropanes will cover the spectral range extending from the vacuum-ultraviolet to the infrared region. 

The experimental spectrum of ethylene (cf. Mulliken, 1977) shows a broad absorption band in the vacuum UV region, at 180-145 nm. This has been assigned to a V<-N or transition with superimposed Rydberg... 

The wavelength range is divided into several sections which are shown in Table 4. As far as this discussion of sources is concerned, the range is divided into two the vacuum uv region is treated separately. 

Electron (or UV-VIS) spectroscopy is the oldest spectroscopic technique applied in chemistry ". In non-conjugated tertiary heterocyclic amines the n -mt UV absorption is observed around 213 to 218 nm with an extinction coefficient ( , ) at of 1600 to 3100. Additional long-wavelength absorptions around 260 nm have been reported, but these bands are much weaker in intensity with below 100. The n n transition of alkenes between 163 and 197 nm is located in the vacuum-UV region which is experimentally difficult to measure (ethene = 163 nm, =... 

Table 1 summarizes the different types of radiation as well as the corresponding wavelengths, the energy of one photon and the type of transformation they can induce in matter. It can be seen that X- and 7-photons have energies greatly in excess of the bond energies and first ionization potentials of simple molecules and radicals (Table 2). The UV photons of wavelength longer than 2000 A are often sufficiently energetic to cause dissociation but cannot produce ionization. Ionization, however, can often be produced efficiently in the vacuum UV region.

The excitation of saturated silanes168,170,171 and disilanes172- 174 in the vacuum UV region and their mercury-sensitized photolysis175,176 also lead to silyl radicals, some of which then subsequently undergo hydrogen atom abstraction to yield silenes. This excitation also opens other paths toward silene products when the photolysis is performed at high temperatures. 

Note that we have been discussing lamps utilizing 254 nm. photon as an excitation energy. Since we have already discussed HPMV lamps which utilize 254-413 nm radiation to excite phosphors (see above), we are now ready to explore the vacuum-UV region which uses photons generated at 147 nm to 173 nm wavelengths to excite phosphor display devices. These include 2 types, plasma display panels (POP) and Neon Signs. 

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