Trapped emission

Fig. 2. Absorption (upper) and fluorescence spectra (lower) of anthracene single crystal doped with 2-hydroxyanthracene at about 6K. The X-trap frequencies in absorption and emission are nearly coincident. The X-trap emission is displaced from the X origin by 397 cm-1, showing the emission to be that of a host molecule. Os and 69 belong to the two sites of 2-hydroxyanthracene guests. Reprinted from Chemical Physics Letters, 31, by Brillante, Craig, Mau and Rajikan, Optical Absorption by X-traps in Anthracene pp. 215-219 (1975), with the kind permission of Elsevier Science - NL, Sara Burgerhartsstraat 25, 1055 KV Amsterdam, The Netherlands.

On the other hand, the excimer emission because it is 80% non-correlated with monomer trap emission and because it is effectively quenched in the copolymers even at low temperatures, must largely arise from a mobile precursor. The activation energy for hopping of this precursor is implied to be <10 cm l. This is not unreasonably low(12,17), and indeed, the zero-point energy of the phenyl chromo-phore could in principle allow completely activationless hopping (tunneling) at reasonable rates. Determination of the true situation will require measurements at still lower temperatures, which are now in progress. We note that the polystyrene emission spectrum at 4.2K reported in (Id) indicates a monomer/excitner intensity ratio nearly the same as our 20K spectra. 

Keywords Triplet emitters OLED Organic/organometallic light emitting diode Exciton trapping Emission properties Electroluminescence Electrophosphorescence ... 

Smoke from forest fires may be collected by various means for subsequent laboratory analysis. The most applicable approach is to trap emissions from biomass burning on absorbent material. The absorbent material is then either solvent-extracted for GC analysis or directly desorbed onto a GC. For example, smoke is pulled with an air pump at a rate of 10-50mLmin through triple-layer glass cartridges with separate... 

Stock and Yersin [221] reported polarized emission spectra up to 23 kbar for single crystals of Ba[Pt(CN)4] 4H2O. At ambient pressure, the intrachain Pt-Pt separation is 3.32 A and the peaks of the free exciton and self-trapped emission... 

The effect of temperature on deep trap emission is similar to that observed for bandgap emission, with the intensity of the emission decreasing as the temperature increases. This can be explained by the involvement of nonradiative recombination processes dominating at higher temperature. Nonradiative relaxation in CdSe nanoclusters has been assigned to the involvement of a multiphonon relaxation mechanism mediated by a vibrational mode of the surface phenylse-lenolate ligands. ... 

At the centre of the lonotron was a piece of metal foil that was impregnated with radium and then coated to trap emissions of radon gas. The foil was mounted in an aluminum housing, which provided shielding and directed the radiation. The lonotron could be fabricated in different sizes but was usually long and narrow. In a typical installation it would bridge the width of a conveyer belt at a distance from one to three inches over the moving material. Tariffs had a significant impact on how Eldorado structured its lonotron deal with U.S. Radium. After some discussions, customs allowed Eldorado to ship radium to the United States duty-free if it were destined to return to Canada as part of an lonotron. Still, Eldorado had to partially assemble the device to evade a Canadian tariff on a fully assembled product. ... 

Coming back to CdS NRs in smectic LCP matrix (Fig. 15.4), we will further summarize what is going on with PL. The position of the CdS NRs emission peak in an LCP matrix is nearly the same as it is in a homogeneous solution (Fig. 15.7a). The number of defects is much higher than in CdS NRs in solution and the trap emission is also very high. When the PL of CdS NRs in LCP matrix has been induced at a wavelength longer than the PL emission peak (Ezhov et al. 2011) an... 

In 1997, Chen and co-workers were the first to report the TL of a ZnS nanoparticle [161]. They prepared the ZnS nanoparticles using Zn(NOs)2 and NaiS as sources, and these nanoparticles were deposited on a quartz substrate for measurements. The average sizes of ZnS nanoparticles were estimated from the Debey-Scherrer formula and using XRD. The size of the nanoparticles prepared at RT, 50, 100, and 200 C, were 1.81, 2.50, 2.74 and 3.01 nm, respectively. Fig. 29 (a) illustrates the luminescence spectra of ZnS nanoparticles. It is seen that the luminescence intensity of trapped emission increases with decreasing size of the nanoparticles and the emission is blue-shifted as the size reduces. Fig. 29 (b) shows the thermoluminescence glow curves of the ZnS Mn nanoparticles. It is evident that the glow peak occurs around 360 K. It is to be noted that all samples show the glow peaks at almost the same position and the TL intensity is consistent with that of the surface fluorescence [161]. 

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