UV wavelength region

Fig. 1. Main laser lines resp. wavelength ranges (lower part) and absorption ranges of some characteristic biomolecules resp. fields of action in photomedicine (upper part) in the visible and UV wavelength region. As a survey the spectra are shown in the ranges of their main maxima only (see also text).

The phenomenon of differences between the absorption of left- and of right-circularly polarised light is not restricted to the visible and UV wavelength regions, so infrared and Raman CD are likely to yield even more sophisticated information... 

Organic thin-film lasers with such a plastic substrate and the Spiro compound Spiro-40F as active medium have been shown [59]. This demonstrates the feasibility of the fabrication of low-cost organic DFB lasers in the UV-wavelength region. 

Proposed mechanisms of action of UV stabilizers are UV absorption, excited-state quenching, hydroperoxide decomposition and radical scavenging. For HAS the only mechanism that can be ruled out is UV absorption, because many very effective HAS stabilizers as, for example, LMW-HALS-1 do not absorb in the UV wavelength region... 

The same principle can also be used with a reversible fluorescent indicator, in which case the concentration of one of the indicator forms is measured by its fluorescence rather than absorbance intensity. Light in the blue or UV wavelength region excites the fluorescent dye to emit longer wavelength light, and the two forms of the dye may have different excitation or emission spectra to allow their distinction. 

The UV wavelength region causing photodegradation of the polymer formulation. 

The applicability of the liquid crystals of type I for optical experiments is limited due to the strong absorption of these molecules in the near ultraviolet (uv) wavelength region. The cholesteryl derivatives (II)... 

Direct fluorescence, phosphorescence and X-ray fluorescence spectroscopy for polymer/additive analysis have been reported [513]. In commercial polymers, additives having electronic absorption bands in the visible and near-UV wavelength regions may fluoresce and give rise to composite spectra. Some general applications of fluorescence spectroscopic analysis for polymeric materials relate to ... 

The complete dissociation of the hydrocarbons [l 2 ], [28" 2 ] and [40" 2 ] in DMSO has been demonstrated by quantitative generation of both Kuhn s carbanion [2 ] and carbocations [1" ], [28" ] and [40" ] as determined by UV-vis spectra (Table 6 and Eig. 4). However, since carbocation [24 ] has no absorptions at a wavelength region longer than 220 nm in the UV spectrum, there remained an ambiguity that this cation might have decomposed in the DMSO solution. A clue to this problem could be obtained by determination of the electric conductivity of DMSO solutions of hydrocarbon salts (Table 7) (Okamoto et al., 1990). 

UV/VIS absorption spectroscopy, pioneered by Beckman (1941), is one of the oldest and most widely used instrumental techniques, despite being regarded by some analysts as obsolete. Recently there has been a renaissance in UV spectroscopy with many new techniques, instruments and data processing methods [8]. Modem highest specification UV/VIS absorption and fluores-cence/phosphorescence spectrometer instruments extend their wavelength region from the far UV (175 nm) into the NIR region (1100 nm). Small footprint UV/VIS spectrometers (200-1100 nm) are now available. Paul [9] has traced the history of UV/VIS instrumental developments. 

Differential photocalorimetry (DPC) is included here since the instrument used is essentially an adaptation of DSC instrumentation. The photocalorimeter comprises a DSC instrument with a UV/visible source mounted on top, such that light of appropriate wavelength or wavelength region from the source is focused onto the measuring head (both reference and sample pans). The most frequent use of DPC is in the study of polymer cure reactions, but it may also be used to follow such as UV degradation. 

---