Multilayer fluorescence emission

Summary. This Chapter focuses on the investigation of fast electron transport studies in solids irradiated at relativistic laser intensities. Experimental techniques based upon space-resolved spectroscopy are presented in view of their application to both ultrashort Ka X-ray sources and fast ignition studies. Spectroscopy based upon single-photon detection is unveiled as a complementary diagnostic technique, alternative to well established techniques based upon bent crystals. Application of this technique to the study of X-ray fluorescence emission from fast electron propagation in multilayer targets is reported and explored as an example case. 

The lifetimes of molecular fluorescence emissions are determined by the competition between radiative and nonradiative processes. If the radiative channel is dominant, as in the anthracene molecule, the fluorescence quantum yield is about unity-and the lifetime lies in the nanosecond range. In molecular assemblies, however, due to the cooperative emission of interacting molecules, much shorter lifetimes—in the picosecond or even in the femtosecond range—can theoretically be expected an upper limit has been calculated for 2D excitons [see (3.15) and Fig. 3.7] and for /V-multilayer systems with 100 > N > 2.78 The nonradiative molecular process is local, so unless fluorescence is in resonance by fission (Section II.C.2), its contribution to the lifetime of the molecular-assembly emission remains constant it is usually overwhelmed by the radiative process.118121 The phenomenon of collective spontaneous emission is often related to Dicke s model of superradiance,144 with the difference that only a very small density of excitation is involved. Direct measurement of such short radiative lifetimes of collective emissions, in the picosecond range, have recently been reported for two very different 2D systems ... 

The SPGCE is based on the fluorescent emission from the organic Alqs molecules in the active layer and its diffraction in a periodically modulated surface with possible SPPs enhancement due to multilayer structure of metallic thin film. 

Similar strategies have been followed to obtain white emission from fluorescent polymer systems and phosphorescent ones as well. However, polymer blends have generally been used to fabricated WPLEDs (as multilayer spin-coated polymer assemblies are difficult to obtain owing to close solubility parameters of materials), such as red, green, blue light-emitting three-polymer systems [257-259] and two-... 

Fluorescence of polydiacetylenes was first reported qualitatively by Baughman and Chance, and has also been abserved in multilayers of polymerized 5a While the blue form of polymerized amphiphiles is non-fluorescent, the red form exhibits a strong fluorescence with emission maxima at 570 and 640 nm. The luminescence is likely due to a polymer degradation product formed in disordered areas of the sample In multilayers of 2 the fluorescence quantum yield has been determined to be (2.0 0.5)xl0- >. 

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