Zinc oxide quantum dots embedded films by metal organic chemical vapor deposition

Zinc oxide (ZnO) quantum dots (QDs) were fabricated on silicon substrates by metal organic chemical vapor deposition. Formation of QDs is due to the vigorous reaction of the precursors when a large amount of precursors was introduced during the growth. The size of the QDs ranged from 3 to 12 nm, which was estimated by high-resolution transmission electron microscopy. The photoluminescence measured at 80 K showed that the emission of QDs embedded film ranged from 3.0 to 3.6 eV. The broad near-band-edge emission was due to the quantum confinement effect of the QDs.     

Quantum Dynamics of Oxyhydrogen Complex-Forming Reactions for the HO2 and HO3 Systems

Complex-forming reactions widely exist in gas-phase chemical reactions.Various complexforming bimolecular reactions have been investigated and interesting phenomena have been discovered.The complex-forming reactions usually have small or no barrier in the entrance channel, which leads to obvious differences in kinetic and dynamic characteristics compared with direct reactions.Theoretically, quantum state-resolved reaction dynamics can provide the most detailed microscopic dynamic mechanisms and is now feasible for a direct reaction with only one potential barrier.However, it is of great challenge to construct accurate potential energy surfaces and perform accurate quantum dynamics calculations for a complex polyatomic reaction involving deep potential wells and multi-channels.This paper reviews the most recent progress in two prototypical oxyhydrogen complex-forming reaction systems, HO₂ and HO₃, which are significant in combustion, atmospheric, and interstellar chemistry.We will present a brief survey of both computational and experimental work and emphasize on some unsolved problems existing in these systems.     

Dissipaton Equation of Motion Theory versus Fokker-Planck Quantum Master Equation

The quest of exact and nonperturbative methods on quantum dissipation with nonlinear coupling environments remains in general a great challenge. In this review we present a comprehensive account on two approaches to the entangled system-and-environment dynamics, in the presence of linear-plus-quadratic coupling bath. One is the dissipaton-equation-ofmotion (DEOM) theory that has been extended recently to treat the nonlinear coupling environment. Another is the extended Fokker-Planck quantum master equation (FP-QME) approach that will be constructed in this work, based on its DEOM correspondence. We closely compare these two approaches, with the focus on the underlying quasi-particle picture, physical implications, and implementations.     

Photochemical preparation of tricyclic hydroxyketones by transanular cyclization of bridged 4-benzoylcyclohexanones

Summary The bridged 4-benzoyl-cyclohexanones3a–f were synthesized by ,-annelation of cyclic ketones. Irradiation of3a–f revealed a strong dependence of the photochemical behaviour on the ring size and the introduction of a nitrogen atom. Ketones which are able to form 1,6-biradicals (3b,c,e) undergo unselective photolytic decomposition, whereas3a,d,f afforded tricyclic hydroxyketones. The diastereoselectivity of ring closure is remarkably improved by introduction of a protected nitrogen atom (3d,f) in comparison to the carbocyclic diketone3a. Moreover, the N protective group of 4-azatricyclo-4.3.1.0^3,8]decan-7-one (7) could be removed affording the free hydroxy amino ketone8 in good yields. An explanation of the diastereoselective cyclization of3a and of the surprisingly low quantum yield of3d was found by conformational analysis of the corresponding triplet biradicals.

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Photochemische Darstellung tricyclischer Ketone durch transanulare Cyclisierung verbrückter 4-Benzoylcyclohexanone

Zusammenfassung Die verbrückten 4-Benzoyl-cyclohexanone3a–f wurden durch ,-Anellierung cyclischer Ketone synthetisiert. Das photochemische Verhalten von3a–f hängt in starkem Maße von der Ringgröße und von der Einführung eines Stickstoffatoms ab. Ketone, die in der Lage sind, 1,6-Biradikale zu bilden (3b,c,e), unterliegen einer unselektiven photolytischen Zersetzung, während3a,d,f tricyclische Hydroxyketone liefern. Die Diastereoselektivität des Ringschlusses wird durch Einführung eines Stickstoffatoms (3d,f) im Vergleich zum carbocyclischen Analogon3a deutlich gesteigert. Weiterhin gelang es, die N-Schutzgruppe im 4-Azatricyclo-[4.3.1.0^3,8]decan-7-on (7) unter Bildung des freien Hydroxyaminoketons8 in guten Ausbeuten zu entfernen. Eine Erklärung für die diastereoselektive Cyclisierung von3a und für die überraschend geringe Quantenausbeute von3d wurde durch Konformationsanalyse der entsprechenden Triplett-Biradikale gefunden.

     

Dirichlet Forms and Dirichlet Operators for Gibbs Measures of Quantum Unbounded Spin Systems: Essential Self-Adjointness and Log-Sobolev Inequality

For each [0, 1] we consider the Dirichlet form and the associated Dirichlet operator for the Gibbs measure of quantum unbounded spin systems interacting via superstable and regular potential. The Gibbs measure is related to the Gibbs state of the system via a (functional) Euclidean integral procedure. The configuration space for the spin systems is given by We formulate Dirichlet forms in the framework of rigged Hilbert spaces which are related to the space . Under appropriate conditions on the potential, we show that the Dirichlet operator is essentially self-adjoint on the domain of smooth cylinder functions. We give sufficient conditions on the potential so that the corresponding Gibbs measure is uniformly log-concave (ULC). This property gives the spectral gap of the Dirichlet operator at the lower end of the spectrum. Furthermore, we prove that under the conditions of (ULC), the unique Gibbs measure satisfies the log-Sobolev inequality (LS). We use an approximate argument used in the study of the same subjects for loop spaces, which in turn is a modification of the method originally developed by S. Albeverio, Yu. G. Kondratiev, and M. Röckner.     

也谈量子力学的基础

本文通过在不同边界条件下动量算符的厄密性和自伴性的区分,给出了对量子力学的一维无限深方势阱中基态粒子的动量分布问题的严格分析,论证了量子力学基本假设的严谨性和自洽性.     

A family of quantum projective spaces and related -hypergeometric orthogonal polynomials

A one-parameter family of two-sided coideals in is defined and the corresponding algebras of infinitesimally right invariant functions on the quantum unitary group are studied. The Plancherel decomposition of these algebras with respect to the natural transitive -action is shown to be the same as in the case of a complex projective space. By computing the radial part of a suitable Casimir operator, we identify the zonal spherical functions (i.e. infinitesimally bi-invariant matrix coefficients of finite-dimensional irreducible representations) as Askey-Wilson polynomials containing two continuous and one discrete parameter. In certain limit cases, the zonal spherical functions are expressed as big and little -Jacobi polynomials depending on one discrete parameter.

     

High Performance (fT~500GHZ) In0.52Al0.48As/In0.53Ga0.47As/InP Quantum Wire MODFETs Employing Asymmetric Coupled-Well Channels

A coupled-well InAlAs/InGaAs quantum wire MODFET structure is proposed, for which simulations predict improved frequency performance (>500 GHz), over a wider range of V_g, as compared to well/wire devices with a standard MODFET heterointerface. A comparison of several transverse potential well profiles, obtained by varying the placement of a thin barrier within a 100 Å finite well, is presented. In all cases, the quantum wires consist of a 0.1 m long channel and a 150 Å finite-square-well lateral profile. It has been found that the peak of the electron distribution for the first confined state, as measured from the heterointerface, changes dramatically depending on the location of the thin barrier. For quantum wire structures, realized in the lattice matched system of In_0.52Al_0.48As/In_0.53Ga_0.47As/InP, a change in the barrier location of 25 Å is accompanied by a shift in the carrier peak of more than 40 Å (~20 Å closer to or farther from the spacer-well interface than in the standard MODFET profile). Implications of this are reflected in the current-voltage characteristics (I_d-V_d) and frequency responses (f_T-V_g) of the proposed structures.     

Characterization of InAs quantum dots on lattice-matched InAlGaAs/InP superlattice structures

Self-assembled InAs quantum dots (QDs) in an InAlGaAs matrix, lattice-matched to InP substrate, have been grown by molecular beam epitaxy (MBE). Transmission electron microscopy (TEM), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) are used to study their structural and optical properties. In InAs/InAlGaAs/InP system, we propose that when the thickness of InAs layer deposited is small, the random strain distribution of the matrix layer results in the formation of tadpole-shaped QDs with tails towards random directions, while the QDs begin to turn into dome-shaped and then coalesce to form islands with larger size and lower density to release the increasing misfit strain with the continuous deposition of InAs. XRD rocking curves showing the reduced strain with increasing thickness of InAs layer may also support our notion. The results of PL measurements are in well agreement with that of TEM images.