Luminescent lighting

Keywords. Metal-based dendrimers, electrochemistry, multielectron processes, luminescence, light harvesting. 

For over 50 years the phosphors of choice for luminescent lighting have been based on activated calcium halophosphates, Ca3(PO )3X (where X = F, Cl), the usual activators being Sb " and Mn ". When Sb " is used as the dopant the phosphor is a very efficient blue emitter under 254 nm excitation, whilst Mn shows an orange... 

The intensity of the incident beam B is reduced to that of the transmitted beam Bt through scattering (S), luminescence (L) and absorption (A). Assuming that the incident beam follows a well defined path, the scattered light and the luminescence light are emitted in all directions. 

Up-conversion. It is also possible to add the laser light of frequency vL to some other light, for instance luminescence light of frequency vF to obtain a whole spectrum of frequencies vL + vF. The two beams of light are mixed... 

Up-conversion. This is similar to autocorrelation, but the laser pulse is mixed with the luminescence light of a sample in an SHG crystal to generate light of frequency vL + vE. The time between the laser pulse (vL) and the luminescence emission (vE) is varied by means of an optical delay path, and the light of added frequency is detected by a usual PM tube via optical filters. 

Tungsten chemicals find limited use in inks, paints, enamels, dyes, and glass manufacture. Some tungsten compounds and their derivative phosphors find use in x-ray screens, television picture tubes, and luminescent light sources. 

The quantiun yield of luminol is relatively low and developments now in progress use the luminescent light source to excite a secondary fluorescent molecule. Luminescence, like fluorescence, is susceptible to quenching by a vM iety of drugs and endogenous compounds. 

Like helium, neon forms no compounds, but it is a very useful element. For example, neon is widely used in luminescent lighting (neon signs). Argon, which recently has been shown to form chemical bonds under special circumstances, is used to provide the noncorrosive atmosphere in incandescent light bulbs, which prolongs the life of the tungsten filament. 

If the luminescent light is to be polarized, it is necessary, first, that the emission of each elementary oscillator should be anisotropic in intensity, depending on the orientation of the emitter with respect to the direction of observation of luminescence, and the distribution of excited oscillators should be anisotropic with respect to the direction of observation. 

The results of the theoretical analysis in Sect. 1.2 show that in the study of relaxation processes in solutions of polymers containing luminescent markers (LM) much information is provided by the dependence of the reciprocal value of the polarization of luminescent light of the polymer solution, 1/p, on the viscosity of the solvent tj, 1/p =/(T/t ), measured at constant temperature T. Theoretical analysis of Eq. (1.2.10) shows that for macromolecules in solution in which all the relaxation processes occur at times Tj >Tf (t/ is the lifetime of luminescence) the following equation is valid for the average time r i (see Sect. 1.2) (Eq. 2.1) 1... 

The investigation of the intramolecular mobility (I MM) of macromolecules by the method of polarized luminescence (PL) is based on the study of the characteristics of luminescent light (polarization of luminescence and lifetime in the excited state) of luminescent groups bonded to the investigated macromolecules. 

Photoluminescence spectra have b een measured at room temperature using a semiconductor laser as an excitation light source (10 W/cm at 980 run). Luminescence light has been collected by a lens condenser and then dispersed with a grating monochromator (MDR-23). Light detection was performed by a germanium photodiode DPD 2000 (Dilas Co.). A silicon filter was used to additionally cut off the excitation radiation. 

Another application that benefits from the small pores and large inner surface of aerogels are photo-luminescent light sources [83]. Until now, in these devices a radioactive gas (e.g., tritium) was let into a glass tube coated with a phosphor at the inner surface. Integrating the phosphor in an aerogel of low density increases both the intensity and total output of the system. 

Polymer Blends. Let us now apply this technique to the study of polymer blends. We will assume that the two materials have different sets of (mechanical) transition temperatures and that energy spectra of the luminescent light given off by the two polymers are distinguishably different. If the two polymers are completely miscible on a molecular scale (a rare event indeed), we can expect that many of the luminescence maxima will be seen at temperatures different from those of the blend components. This will certainly apply to the Tg of the miscible blend which can be approximated by ... 

Luminescent lighting started even before the Second World War. The ultraviolet radiation from a low-pressure mercury dischaige is converted into white light by a phosphor layer on the inner side of the lamp tube. These lamps are much more efficient than the incandescent lamp a 60 W incandescent lamp yields 15 Im/W, a standard 40 W luminescent lamp 80 Im/W. 

We u.se the term luminescent lighting instead of the generally used fluorescent lighting, since most of the luminescent materials that are used do not show fluorescence (which is defined as an emission transition without spin reversal, i.e. AS = 0 see also Appendix III). 

A luminescent lighting lamp has to emit white light, so that the sun, our natural lighting source, is imitated. The sun is a black body radiator, so that its emission spectrum obeys Planck s equation ... 

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