Structural dynamics in quantum solids. II. Real-time probing of the electronic bubble formation in solid hydrogens

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Lattice vibrations within crystalline solids, or phonons, provide information on a variety of important material characteristics, from thermal qualities to optical properties and phase transition behavior. When the material contains light ions or is subjected to sufficiently low temperatures and/or high pressures, anharmonic and nuclear quantum effects (NQEs) may significantly alter its phonon characteristics. An accurate method, combining the quantum correlator approach with path integral molecular dynamic

Cavity quantum electrodynamics (QED) studies the interaction between atoms and a single electromagnetic mode. When the atoms form a degenerate quantum gas, the resulting lightâ matter interaction reflects the underlying quantum statistics of the particles. Recently, degenerate Fermi gases have been coupled to optical cavities, enabling the exploration of strongly correlated fermionic systems with interactions mediated by cavity photons. Remarkably, when disorder is introduced into such systems, the resulti

Controlling the temporal and kinetic statistics of excitons in semiconductor nanocrystals is important for understanding how multiexcitonic processes emerge in ultrafast excited‐state dynamics under low‐fluence conditions. Under conventional single‐pulse excitation, the Poissonian nature of exciton generation limits the manifestation of biexciton‐mediated processes in the observed kinetics at low fluence. Here, we demonstrate a sequential ultrafast excitation scheme in CsPbBr 3 nanocrystals that reshapes th

Environmental transmission electron microscopy was used to characterize in situ the reduction and oxidation of nickel from a Ni/YSZ solid oxide fuel cell anode support between 300-500°C. The reduction is done under low hydrogen pressure. The reduction initiates at the NiO/YSZ interface, then moves to the center of the NiO grain. At higher temperature the reduction occurs also at the free NiO surface and the NiO/NiO grain boundaries. The growth of Ni is epitaxial on its oxide. Due to high volume decrease, na

A series of imidazolium salts with the nitrile functional group attached to the alkyl side chain, viz. [C(n)CNmim][X] (where C(n)CNmim is the 1-alkylnitrile-3-methylimidazolium cation and C-n = (CH2)(n), n = 1-4; X = Cl, PF6, and BF4) and [C(3)CNdmim][X] (where C(n)CNdmim is the 1-alkylnitrile-2,3-dimethylimidazolium cation and C-n = (CH2)(n), n = 3; X = Cl, PF6, and BF4), have been prepared and characterized using spectroscopic methods. The majority of the nitrile-functionalized imidazolium salts can be cl

The dynamics of electron bubble formation upon excitation of the A(3ss) Rydberg orbital of NO in solid Ne was studied by conventional spectroscopy and fs pump-probe spectroscopy. The fs pump pulse initiates the formation of a bubble by the expansion of the Ne atoms surrounding the NO impurity, generating a wave packet of intermol. NO-matrix modes. The dynamics exhibits a 1st peak due to the sampling of the initial expansion of the bubble followed by >=1 oscillation of the bubble boundaries, which occurs .ap

In a pump-probe experiment, we have been able to control, with phase-locked probe pulses, the ultrafast nonlinear optical emission of a semiconductor microcavity, arising from polariton parametric amplification. This evidences the coherence of the polariton population near k = 0, even for delays much longer than the pulse width. The control of a large population at k = 0 is possible although the probe pulses are much weaker than the large polarization they control. With rising pump power the dynamics of the

Recent developments in the field of first-principles simulation applied to vitreous systems are reviewed. Starting from first-principles molecular dynamics as a basic tool for the generation of structural models, this paper describes how, in recent years, the scope of first-principles methods has extended to the interpretation of vibrational spectra of glasses. (C) 2002 Elsevier Science Ltd. All rights reserved.

We study the subpicosecond gain dynamics in a high-finesse semiconductor microcavity containing quantum wells by means of degenerate pump-probe spectroscopy. Tuning the optical excitation in resonance with both the exciton and the cavity modes, at high pump fields the probe pulses are strongly amplified near the energy of the empty-cavity mode. At zero probe delay, integration of the probe spectrum yields a net gain of several percents. The coherent nature of the gain is demonstrated by its oscillatory beha

The matching pursuit algorithm can be used to derive signal decompositions in terms of the elements of a dictio- nary of time–frequency atoms. Using a structured overcomplete dictionary yields a signal model that is both parametric and signal adaptive. In this paper, we apply matching pursuit to the derivation of signal expansions based on damped sinusoids. It is shown that expansions in terms of complex damped sinusoids can be efficiently derived using simple recursive filter banks. We discuss a subspace e

Transitions from bound atomic Rydberg Stark states in a static electric field to autoionizing Rydberg states above the electric-field-induced ionization threshold are studied using a broadband, tunable free-electron laser (photon energy 160-1400 cm(-1), pulse duration similar to 1 ps) and compared with multichannel quantum defect theory calculations. An atomic streak camera is used to record the time-resolved electron emission transients of the autoionizing atoms. For Stark states located on the downfield s

Hydrogenated amorphous silicon has been prepared at a plasma excitation frequency in the very-high-frequency band at 70 MHz with the glow discharge technique at substrate temperatures between 280 and 50-degrees-C. The structural properties have been studied using hydrogen evolution, elastic recoil detection analysis, and infrared spectroscopy. The films were further characterized by dark and photoconductivity and by photothermal deflection spectroscopy. With respect to films prepared at the conventional fre

In order to achieve selective inversion of a chosen family of sidebands in NMR spectra of solids rotating at the magic angle (MAS spectra), a sequence of so-called DANTE pulses can be applied in synchronization with the sample rotation period. It is shown by simulation and expt. that the profiles of the offset dependence can be greatly improved by varying the amplitudes of the DANTE pulses, so that the envelope corresponds to that of a G3 Gaussian cascade. Alternatively, the DANTE pulses may be replaced by

This paper is concerned with reaction systems in which fuel production is achieved by illumination of aqueous solutions. Research interest in this field focuses on the photoredox reaction A + D [graphic omitted] A–+ D+ in which A and D are solutes of which one is excited by light. Major problems to overcome for practical use of these systems are the retardation of the back reaction and the production of fuel from the intermediates A– and D+. Micellar aggregates may be employed for the kinetic control of for

Structural dynamics in quantum solids. II. Real-time probing of the electronic bubble formation in solid hydrogens

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Anharmonic phonons via quantum thermal bath simulations

Cavity quantum electrodynamics with a Fermi gas in a cavity microscope

Enhanced Contribution of Biexciton‐Mediated Decay Kinetics in Perovskite Nanocrystals Via Sequential Ultrafast Excitation

In situ reduction and oxidation of nickel from solid oxide fuel cells in a Titan ETEM

Synthesis and characterization of ionic liquids incorporating the nitrile functionality

Ultrafast structural dynamics in electronically excited solid neon. I. Real-time probing of the electronic bubble formation

Coherent control of polariton parametric scattering in semiconductor microcavities

First-principles simulation of vitreous systems

Net coherent optical gain in strongly pumped semiconductor microcavities

Matching pursuit and atomic signal models based on recursive filter banks

Decay of oriented Rydberg wave packets excited with far-infrared radiation

Influences of a High-Excitation Frequency (70 Mhz) in the Glow-Discharge Technique on the Process Plasma and the Properties of Hydrogenated Amorphous-Silicon

Shaped pulses for selective inversion of magnetization in solids spinning at the magic angle

Light-induced charge separation and water cleavage in microheterogenous aqueous systems