Results 1 - 10 of 184522
Results 1 - 10 of 184522. Search took: 0.109 seconds
|Sort by: date | relevance|
[en] This conference was organized around 9 sessions: -) single molecule, -) quantum optics, -) hole-burning materials and mechanisms, -) single nano-particle spectroscopy, -) dephasing and spectral diffusion, -) microwave photonics, -) biological systems, -) rare earth doped materials, -) novel laser sources. This document gathers only the slides of the presentations
[en] Upper-valence-band spectra have been obtained by ultraviolet photoemission spectroscopy for several cubic and orthorhombic Pbsub(1-x)Snsub(x)Se single crystals. Some electronic distribution curves - EDCs - are presented to demonstrate the shift of the valence bands with increasing x. The results are discussed in terms of band structure calculations. (author)
[en] The photophysical properties of pyronin B (PyB) and pyronin Y (PyY) in reverse micelles formed with water/sodium bis (2-ethyl-1-hexyl) sulfosuccinate (AOT)/n-heptane were investigated by UV–vis absorption, steady-state and time-resolved fluorescence spectroscopy techniques. This study was carried out a wide range of reverse micelle sizes, with hydrodynamic radii ranging from 1.85 to 9.38 nm. Significant photophysical parameters as band shifts, fluorescence quantum yields and fluorescence lifetimes were determined to understand how photophysical and spectroscopic features of the dye compounds were affected by the variation of reverse micelle sizes. In this regard, control of reverse micelle size by changing W0, the molar ratio of water to surfactant, allowed tuning the photophysical properties of the dyes in organic solvent via reverse micelle. Non-fluorescent H-aggregates of pyronin dyes were observed for the smaller reverse micelles whereas an increase in the reverse micelle size induced an increment in the amount of dye monomers instead of dye aggregates. Thus, the fluorescence intensities of the dyes were improved by increasing W0 due to the predomination of the fluorescent dye monomers. As a result, the fluorescence quantum yields also increased. The fluorescence lifetimes of the dyes in the reverse micelles were determined by the time-resolved fluorescence decay studies. Evaluation of the fluorescence lifetimes calculated for pyronin dyes in the reverse micelles showed that the size of reverse micelle affected the fluorescence lifetimes of pyronin dyes. -- Highlights: • The photophysical properties of pyronin dyes were examined by spectroscopic techniques. • Optical properties of the dyes were tuned by changing of W0 values. • The fluorescence lifetime and quantum yield values of the dyes in reverse micelles were discussed
[en] Intramolecular excimer formation dynamics of Di-9H-fluoren-9-yldimethylsilane (DFYDMS) has been investigate by means of ps time-resolved fluorescence spectroscopy and an ab initio method. When a DFYDMS solution in cyclohexane was excited at 290 nm, a res-shifted fluorescence of λmax = 317 nm is observed, having a long tail ranging up to about 400 nm. The 317 nm species is observed to decay, having a lifetime of 1.7 ns, and the 400 nm species is found to rise (rise time=600 ps) after the irradiation pulse and then to decay, having a lifetime of 7.4 ns. The short component of τ = 1.7 ns is presumably related to a locally excited state, and the longer component of τ = 7.4 ns may correspond to an intramolecular excimer. By the aid of the ab initio calculation, we presume that the rise time of 600 ps corresponds to the excimer formation from a near sandwich conformer.
[en] The genetic algorithms (GAs) are applied to extract the values of parameters that describe the behavior of the asymmetric rotorlike fluorescence probes embedded in the uniaxially ordered system. The capabilities of the GA are enhanced by an application of a simple first order derivative search for the values of the multiplicative factors at each stage of the evolutionary run. The convergence is improved by the help of a gradient-expansion search performed after the GA is done. The potentiality of this approach demonstrates an example concerning the synthetic data set.
[en] The absorption spectrum and the incoherent fluorescence spectrum of the lower transition in an S-configuration three-level atomic system driven by a pair of bichromatic fields is investigated. The transmission of the absorption profile from a multipeaked feature to a single-peak feature is identified. Adjusting the relative phase between the two driving fields, the splitting effects of the spectral peaks occur both in the fluorescence and the absorption spectra. Furthermore, phase modulating can dramatically lead to a great suppression of the amplitudes of the whole absorption spectrum. Physically, this effect is attributed to the phase-sensitive nature of the populations and coherence between the atomic states of the system. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
[en] A new method using the laser-induced fluorescence method was developed to measure the spatial electron density distribution. The local electron density can be determined by observing the intensity ratio of the laser- to the collision-induced fluorescence. A spatial electron density distribution of a helium plasma (Tsub(e) -- 6eV, nsub(e) : 1011-12 cm-3) has been determined by observing the He(31P → 21S) laser-induced fluorescence and the He(31D → 21P) collision-induced fluorescence due to the He(31P → 31D) collisional transfer process with electrons. The comparison of the result with that of a conventional method proves this new method is of practical use in the space-resolved measurements of plasma electron density. (author)
[en] The measurement of fluorescence spectra and the determination of fluorescence quantum yields in transparent samples are conceptually simple tasks, but these procedures are subject to several pitfalls that can lead to significant errors. Available technical reports and protocols often assume that the reader possesses a solid theoretical background in spectroscopy and has ample experience with fluorescence instrumentation, but this is often not the case given the many applications of fluorescence in diverse fields of science. The goal of this tutorial is to provide a didactic treatment of the topic that will hopefully be accessible to readers without extensive expertise in the field of fluorescence. The article covers the theoretical background needed to understand the origins of the most common artifacts researchers can expect. Possible artifacts are illustrated with examples to help readers avoid them or identify them if present. A step-by-step example of a fluorescence quantum yield determination in solution is provided with detailed experimental information to help readers understand how to design and analyze experiments. (tutorial)