A temperature dependence for emission of Eu3+ in cubic nanocrystalline Y2O3:Eu3+ was studied contrast with the polycrystalline powders. The intensity decreased solely elevated under excitation a 580 nm light, while it had maximum at certain 488 light. experimental data were well fitted based on theory considering both thermal activated distribution electrons among FJ7 and quenching effect. results indicated that rate nanocrystals (NCs) faster than polycrystals. nonradiative decay rate, wNR,...

One-dimensional pure cubic Y2O3/Eu3+ nanocrystals (NCs) were synthesized by a hydrothermal method at various temperatures. The NCs prepared 130 °C yielded nanotubes (NTs) with wall thickness of 5−10 nm and outer diameter 20−40 nm. 170 180 nanowires (NWs) diameters ∼100 ∼300 nm, respectively. Their luminescent properties, including electronic transition processes, local environments surrounding Eu3+ ions, electron−phonon coupling, UV light irradiation induced spectral changes have been...

The effects of size and europium concentration on photoluminescence properties La2O2S: Eu3+ nanocrystals (∼20 nm) the corresponding bulk were studied. results indicate that in nanocrystals, absorption edge largely shifted to blue comparison bulk, which was mainly attributed variation phonon-excitation relaxation. Two excitation bands observed, located at ∼250 ∼330 nm, respectively, charge transfer (CT) transitions Eu−O Eu−S. Relative CT transition Eu−O, Eu−S increased greatly with...

We survey the recent advances in theoretical understanding of quantum state resolved dynamics, using title reactions as examples. It is shown that progress was made possible by major developments two areas. First, an accurate analytical representation many high-level ab initio points over a large configuration space can now be with high fidelity and necessary permutation symmetry. The resulting full-dimensional global potential energy surfaces enable dynamical calculations either...

Despite its importance in chemistry, the microscopic dynamics of bimolecular nucleophilic substitution (SN2) reactions is still not completely elucidated. In this publication, a prototypical SN2 reaction (F(-) + CH3Cl → CH3F Cl(-)) investigated using high-dimensional quantum mechanical model on an accurate potential energy surface (PES) and further analyzed by quasi-classical trajectories same PES. While indirect mechanism dominates at low collision energies, direct makes significant...

ZnWO4:Eu3+ nanocrystals were prepared by the hydrothermal method at various temperatures and pH values. Their luminescent properties including excitation emission processes, dynamics, local environments surrounding Eu3+ ions systemically studied. The results indicate that particle size of grows with increasing temperature, while it rarely changes value. bands for Eu3+, which are contributed different components, shift considerably to blue relative intensity blue-green caused tungstate groups...

The mode specific reactivity of the F + CHD3 → HF CD3 reaction is investigated using an eight-dimensional quantum dynamical model on a recently developed ab initio based full-dimensional potential energy surface. Our results indicate prominent resonance structures at low collision energies and absence threshold in probabilities. It was also found that excitation C-D stretching or umbrella has relatively small impact reactivity. On other hand, C-H vibration (v1) shown to significantly...

Calculating the thermal rate constants of elementary combustion reactions is great importance in theoretical chemistry. Machine learning has become a powerful, data-driven method for predicting nowadays. Recently, molecular similarity combined with topological indices were proposed to represent hydrogen abstraction alkane [

In this letter, we report the observation of ultraviolet light-induced change excited charge-transfer band in nanocrystalline Y2O3:Eu3+, which is attributed to rearrangements local environments surrounding Eu3+ ions near surface nanoparticles.

A series of niobate–phosphate and niobate–silicate glasses doped with Eu3+ ions were prepared. The emissions, phonon-side band spectra, fluorescence lifetimes these studied the intensity parameters obtained. temperature dependence emission ion in niobate was investigated. temperature-quenching rates determined. results indicate that glasses, as concentration Nb2O5 increases, covalence becomes stronger, symmetry lower electron-phonon coupling strength stronger. Thus, become shorter,...

PbWO4: Er3+,Yb3+ nanocrystals (∼100 nm) were prepared by the hydrothermal method at different pH values (pH = 4, 7, and 9). Their structure luminescence properties under 978-nm laser-diode excitation studied. The results indicate that practical ratio of W to Pb in doping concentration Yb3+ depended strongly on value due change. In upconversion, red (4F9/2→4I15/2) green (2H11/2,4S3/2→4I15/2) emissions observed, both which occurred via a two-photon populating process. Biexponential...

The core-shell rare earth (RE) doped nanophosphors are attracting current interests owing to their potential application in bio-images. Understanding the modification of structure on photoluminescent (PL) properties RE ions is important obtaining efficient nanophosphors. In this paper, Y2O3:Eu3+@SiO2 composites with fixed cubic Y2O3:Eu3+ core (∼80 nm) and controllable thickness silica shell (∼3−21 were synthesized via a modified Stöber method characterized by x-ray diffraction patterns,...

The quantum dynamics of water dissociative chemisorption on the rigid Ni(111) surface is investigated using a recently developed nine-dimensional potential energy surface. dynamical model includes explicitly seven degrees freedom D2O at fixed sites, and final results were obtained with site-averaging model. mode specificity in site-specific reported analyzed. Finally, approximate sticking probabilities for various vibrationally excited states are considering lattice effects formally all nine...

A reaction typically involves a few active modes while the other are largely preserved throughout as spectators. Excitation of an mode is expected to promote reaction, but depositing energy in spectator has no effect, because differing ability for flow coordinate. In this work, we report surprising case specificity key radical-radical OH + HO2 → H2O O2, where such canonical expectations fail hold. Despite its nature, vibrational excitation reactant shown at low collision energies enhance...

The hydrogen abstraction reactions of the hydroxyl radical with alkanes play an important role in combustion chemistry and atmospheric chemistry. However, site-specific reaction constants are difficult to obtain experimentally theoretically. Recently, machine learning has proved its ability predict chemical properties. In this work, a approach is developed temperature-dependent rate title reactions. Multilayered neural network (NN) models by training 11 reactions, several schemes designed...

Abstract Experimental characterization of the transition state poses a significant challenge due to its fleeting nature. Negative ion photodetachment offers unique tool for probing states and their vicinity. However, this approach is usually limited Franck-Condon regions. For example, high-lying Feshbach resonances with an excited HF stretching mode ( v = 2-4) were recently identified in transition-state region F + NH 3 → 2 reaction through photo-detaching FNH − anions, but direct failed...

The dynamics of the hydrogen abstraction reaction between methane and hydroxyl radical is investigated using an initial state selected time-dependent wave packet method within a six-dimensional model. ab initio calibrated global potential energy surface Espinosa-García Corchado was used. Integral cross sections from several low-lying rotational states both reactants have been obtained centrifugal sudden J-shifting approximations. On empirical surface, excitation has little effect on section,...

The dynamics and mode specificity of the HCl + OH → Cl H2O reaction are investigated using a full-dimensional quantum method on an accurate global potential energy surface. It is shown that vibrational excitation reactant greatly enhances reactivity while has little effect. surprising enhancement this early barrier contradicts naive extension Polanyi's rules, but can be explained by sudden vector projection model, which attributes promotional effect vibration to its strong coupling with...

The vibrational and rotational mode specificity of the Cl + H2O → HCl OH reaction is studied on a recently constructed ab initio based global potential energy surface using an initial state selected Chebyshev real wave packet method. full-dimensional quantum dynamical results under centrifugal sudden and/or J-shifting approximations indicate that this enhanced strongly by excitations stretching modes reactant but only weakly bending excitations. On other hand, combination are found to...

The quasi-classical trajectory predicts the rate coefficient of OH + HO₂→ H₂O O₂reaction based on a full dimensional accurate PIP-NN PES, which is fit to 108 000 points calculated at CCSD(T)-F12a/AVTZ level.

Identifying atomic-level mechanisms in elemental chemical reactions is crucial for understanding complex reaction processes. This study focuses on the typical multichannel H + NH2Cl reaction, which plays a significant role environmental science. High-level ab initio calculations determined seven distinct pathways, leading to three product channels: H2 NHCl, HCl NH2, and Cl NH3. A full-dimensional, globally accurate potential energy surface was constructed by fitting 143,333 points,...

We propose a genetic local search algorithm (GLSA) for the optimization design of diffractive optical elements (DOE's). This hybrid incorporates advantages both (GA) and techniques. It appears better able to locate global minimum compared with canonical GA. Sample cases investigated here include binary-phase Dammann gratings, continuous surface-relief grating array generators, uniform top-hat focal plane intensity profile generator. Two GLSA's whose incorporated techniques are hill-climbing...