Ultrafast Dynamics of Intersubband Relaxation in Gaas Quantum-Wells - Hot-Carrier and Phonon Populations Effects

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Singlet and triplet excited-state energies are fundamental to a variety of processes and applications of organic semiconductors, such as singlet fission, triplet-triplet annihilation, and thermally activated delayed fluorescence. Measuring the triplet energy via traditional optical methods is often challenging though, due to spin selection rules governing these excited states following optical excitation. Here we examine cathodoluminescence (CL) spectroscopy in an electron microscope as a candidate to circu

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Branching fraction ratios between the decays

{B}_{(s)}^0\to J/\psi {\eta}^{\left(\prime \right)}

are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The measured ratios of these branching fractions are $ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({B}^0\to J/{\psi \eta}^{\prime}\right)}{\mathcal{B}\left({B}^0\to J/\psi \eta \right)}=0.48\pm 0.06\pm 0.02\pm 0.01,\

Carrier transport and capture paths via barriers of different dimensionality in AlGaAs/GaAs quantum wire (QWR)/quantum dot (QD) heterostructures, grown in inverted pyramids, are studied by photoluminescence (PL) spectroscopy. Evidence for thermally activated diffusion related to potential disorder in the QWR barriers and thermionic emission of carriers from the QD into the QWR barrier is observed in temperature dependent PL spectra. Similar activation energies for the thermionic emission are derived from th

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We perform a detailed analysis of baryon asymmetry generation in the NuMSM (an extension of the Standard Model by three singlet Majorana fermions with masses below the Fermi scale). Fixing a number of parameters of the NuMSM by the neutrino oscillation data, we determine the remaining domain of the parameter space from the requirement of successful baryogenesis. We derive, in particular, the constraints on the mass splitting of a pair of singlet fermions, and on the strength of their coupling to ordinary le

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We investigate n-i-p/n-i-p micromorph tandem cells deposited at process temperature below 200°C in order to be compatible with low Tg (

We present a theoretical and experimental study of a multilayer organic light emitting device (OLED) with a partially doped emission layer. An extended version of our established "MOLED" device model is used to understand the effects of the partially doped layer on the transport behavior and on the radiative charge recombination distribution as a function of applied bias. A step by step discussion of the possible mechanisms that can be introduced by doping and the resulting changes on the device properties

Femtosecond luminescence measurements combined with pump-probe experiments using selective excitation of either free carriers or excitons have been performed. The time-resolved luminescence spectra show a striking disparity compared with recently published theoretical models. Large differences in the pump-probe spectra are observed for resonant and non-resonant (continuum) pumping. The origin of these differences is discussed.

Properties of carrier-induced ferromagnetism in modulation-doped quantum wells of p-type (Cd,Mn)Te are assessed by photoluminescence (PL) and PL excitation spectroscopy. Well-chosen illumination makes it possible to deplete the quantum well and thus to control the strength of the ferromagnetic interactions. Spontaneous local magnetization is proportional to the hole concentration p but the Curie temperature T-C varies little over a wide p range, in agreement with the mean-field model for 2D systems. The spa

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Using luminescence upconversion with 100 fs resolution, we have investigated the intersubband scattering of electrons in GaAs quantum wells (QWs). The energy separations between the first and second confined electron subband (E(12)) were more or less than the LO phonon energy (E(LO)) In narrow QWs (E(12) > E(LO)) the intrinsic LO phonon scattering rate is found to be 1.6 x 10(12) s(-1). A Monte Carlo simulation allows us to reproduce the experimental data with high accuracy. In wide QWs (E(12) < E(LO)) We f

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In a recent paper we measured the lateral hole diffusion in a GaAs/AlGaAs single quantum well (SQW) by a novel method. At helium temperature, we estimate a lateral hole diffusion length in the QW of 1.5 mum. However, the assumption that diffusion takes place mainly in the, SQW needs to be checked, as the measured diffusion length is the result of two competing processes: (i) hole diffusion in the SQW plane itself and (ii) hole diffusion in the barrier followed by recombination in the SQW. We present here a

GaAs/AlxGa1-xAs multiple-quantum-well structures with identical well thicknesses (almost-equal-to 119 angstrom) but with different Al contents x in the barrier (x almost-equal-to 0. 1, 0.2, 0.45, and 1) were grown by molecular-beam epitaxy. We report the characterization of the structures by a combination of different techniques. The x-ray-diffraction technique allows us to estimate the Al content x and to measure the period of the structure with good accuracy. Using the photographs given by high-resolution

Ultrafast Dynamics of Intersubband Relaxation in Gaas Quantum-Wells - Hot-Carrier and Phonon Populations Effects

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