Charge symmetry as an off-shell constraint on the nuclear force for finite range transformations

An upper bound on the variation of the Coulomb subtracted pp scattering length in the ¹S₀ state is obtained for arbitrary unitary and Baker transformations of finite range. It is shown that this variation is always less than the experimental error in the nn scattering length, if the range of the transformation is less than about 1 fm, implying that Sauer's charge symmetry constraint is then automatically fulfilled. This also means that the charge symmetry principle is most relevant for the intermediate range of the nuclear force. We also discuss the zero-energy off-shell parameters which are actually constrained by charge symmetry and a knowledge of the outer part of the interaction.     

Quantum size effects of CO reactivity on metallic quantum dots

We study the reactivity of a metallic quantum dot when exposed to a gas phase CO molecule. First, we perform a Newns-Anderson model calculation in which the valence electrons of the quantum dot are confined by a finite potential well and the molecule is characterized by its lowest unoccupied molecular orbital in the gas phase. A pronounced quantum size effect regarding the charge transfer between the quantum dot and molecule is observed. We then perform a first-principles calculation for a selected size interval. The quantum dot is described within the jellium model and the molecule by pseudopotentials. Our results show that the charge transfer between the quantum dot and the molecule depends critically on the size of the quantum dot, and that this dependence is intimately connected with the electronic structure. The key factor for charge transfer is the presence of states with the symmetry of the chemically active molecular orbital at the Fermi level.     

The symmetry,inferable from Bogoliubov transformation,between processes induced by a mirror in two-dimensional and a charge in four-dimensional space-time

We consider the symmetry between creation of pairs of massless bosons or fermions by an accelerated mirror in (1+1)-dimensional space and emission of single photons or scalar quanta by an electric or scalar charge in (3+1)-dimensional space. The relation of Bogoliubov coefficients describing the processes generated by a mirror to Fourier components of the current or charge density implies that the spin of any disturbances bilinear in the scalar or spinor field coincides with the spin of quanta emitted by the electric or scalar charge. The mass and invariant momentum transfer of these disturbances are essential for the relation of Bogoliubov coefficients to invariant singular solutions and the Green functions of wave equations for both (1+1)-and (3+1)-dimensional spaces, and especially for the integral relations between these solutions. One of these relations leads to the coincidence of the self-action changes and vacuum-vacuum amplitudes for an accelerated mirror in two-dimensional space-time and a charge in four-dimensional space-time. Both invariants of the Lorentz group, spin and mass, play an essential role in the established symmetry. The symmetry embraces not only the processes of real quanta radiation, but also the processes of the mirror and charge interactions with fields carrying spacelike momenta. These fields accompany their sources and determine the Bogoliubov matrix coefficients α _ω′ω ^{B, F} . It is shown that the Lorentz-invariant traces ±trα^B,F describe the vector and scalar interactions of the accelerated mirror with a uniformly moving detector. This interpretation rests essentially on the relation between propagators of the waves with spacelike momenta in two-and four-dimensional spaces. The traces ±trα^{B, F} coincide with the products of the mass shift Δm_{1, 0} of the accelerated electric or scalar charge and the proper time of the shift formation. The symmetry fixes the value of the bare fine structure constant α₀=1/4π.     

N，N-二甲基苯胺和苯醌间光诱导电荷转移

研究了N ,N 二甲基苯胺和苯醌间光诱导电荷转移的溶剂效应 .首先在B3LYP/ 6 31G 水平上对给体和受体进行构型优化 ,然后采用优化的给受体构型在Cs 对称性下计算得到两种相对稳定的复合物构象P和T .在CIS/ 6 31+G 水平上计算复合物气相激发态 ,结果发现 ,构象P的第三单重激发态发生分子间的完全电荷分离 ,构象T的第三激发单重态发生分子间的部分电荷分离 .在上述同样水平上计算复合物溶剂条件下的激发态性质 ,与气相结果相比表明 ,溶剂中两种构象的第三单重激发态均发生完全电荷分离 ,吸收光谱均发生较大红移 .     

A Gauge Invariant Description for the General Conic Constrained Particle from the FJBW Iteration Algorithm

We consider a second-degree algebraic curve describing a general conic constraint imposed on the motion of a massive spinless particle. The problem is trivial at classical level but becomes involved and interesting concerning its quantum counterpart with subtleties in its symplectic structure and symmetries. We start with a second-class version of the general conic constrained particle, which encompasses previous versions of circular and elliptical paths discussed in the literature. By applying the symplectic FJBW iteration program, we proceed on to show how a gauge invariant version for the model can be achieved from the originally second-class system. We pursue the complete constraint analysis in phase space and perform the Faddeev-Jackiw symplectic quantization following the Barcelos-Wotzasek iteration program to unravel the essential aspects of the constraint structure. While in the standard Dirac-Bergmann approach there are four second-class constraints, in the FJBW they reduce to two. By using the symplectic potential obtained in the last step of the FJBW iteration process, we construct a gauge invariant model exhibiting explicitly its BRST symmetry. We obtain the quantum BRST charge and write the Green functions generator for the gauge invariant version. Our results reproduce and neatly generalize the known BRST symmetry of the rigid rotor, clearly showing that this last one constitutes a particular case of a broader class of theories.     

MMgF_4：Eu（M＝Ca，Sr，Ba）体系中铕离子的发光中心及价态

合成了铕离子激活的ＭＭｇＦ４．磷光体，研究了Ｅｕ３＋离子的光谱特征与基质化合物的关系，存在三类发光中心，讨论了基质组成对铕离子价态的影响。     

Relation between proton and neutron asymptotic normalization coefficients for light mirror nuclei and its relevance to nuclear astrophysics

We show how the charge symmetry of strong interactions can be used to relate the proton and neutron asymptotic normalization coefficients (ANCs) of the one-nucleon overlap integrals for light mirror nuclei. This relation extends to the case of real proton decay where the mirror analog is a virtual neutron decay of a loosely bound state. In this case, a link is obtained between the proton width and the squared ANC of the mirror neutron state. The relation between mirror overlaps can be used to study astrophysically relevant proton capture reactions based on information obtained from transfer reactions with stable beams.     

Theory of photoinduced charge separation in solids

We discuss photoinduced ionization and charge separation kinetics in solutions as a way to conserve and utilize light energy. Our interest is in the secret of the high efficiency of reaction centers and the fast and irreversible separation of ions involved in reduction and oxidation reactions in the macromolecule. We present a new theory of reversible charge transfer, which shows high efficiency of charge separation: the charge's recombination has a weak influence on the donor cation-state probability's maximum value but a large effect on its long-time behavior. We give the comparison of new results with recently published ones on charge separation kinetics in condensed media. We use the methods of independent reaction “vessels” and “conditional concentrations”. The influence of back charge transfer is essential for long-time tail of the cation-state probability; its action on the cation-state probability's maximum value grows weak with an increase of forward rate constants and acceptor's concentration.     

Electron energy-loss spectroscopy of tetracyanoquinodimethane,TCNQ, tetrathiafulvalene,TTF, and the salt TTF-TCNQ

Energy loss spectra of low energy electrons (ELS) have been obtained for thin solid films of tetracyanoquinodimethane (TCNQ), tetrathiafulvalene (TTF), and the charge transfer salt TTF-TCNQ as a function of incident energy (20 to 100 eV). The incident energy dependence of energy loss features allows the identification of triplet and symmetry forbidden excitations in TCNQ and TTF. The ELS spectrum of TTF-TCNQ is compared with high energy electron loss data to show that the surface of evaporated films of TTF-TCNQ contains 20–50% neutral TCNQ molecules.     

Topological spin Hall states, charged skyrmions, and superconductivity in two dimensions

We study the properties of two dimensional topological spin Hall insulators which arise through spontaneous breakdown of spin symmetry in systems that are spin rotation invariant. Such a phase breaks spin rotation but not time reversal symmetry and has a vector order parameter. Skyrmion configurations in this vector order parameter are shown to have an electric charge that is twice the electron charge. When the spin Hall order is destroyed by condensation of Skyrmions superconductivity results. This may happen either through doping or at fixed filling by tuning interactions to close the Skyrmion gap. In the latter case the superconductor-spin Hall insulator quantum phase transition can be second order even though the two phases break distinct symmetries.     

Reactions with Weakly Bound Nuclei,at near Barrier Energies,and the Breakup and Transfer Influences on the Fusion and Elastic Scattering

We present a brief review of the reaction mechanisms involved in collisions of weakly bound projectiles with tightly bound targets, at near-barrier energies. We discuss systematic behaviors of the data, with emphasis in fusion, breakup, nucleon transfer and elastic scattering. The dependence of the breakup cross section on the charge and mass of the target is discussed, and the influence of the breakup channel on complete fusion is investigated. For this purpose, we compare reduced fusion cross sections with a benchmark universal curve. The behaviors observed in the comparisons are explained in terms of polarization potentials and of nucleon transfer followed by breakup. The influence of the breakup process on elastic scattering is also discussed. Some apparent contradictions between results of different authors are explained and some perspectives of the field are presented.     

Interacting boson-fermion model of collective states I,the Spin (6) limit

We discuss in detail one of the three possible spinor symmetries of the interacting boson-fermion model. This symmetry, Spin (6), arises when the bosons have SO(6) symmetry and the fermions occupy a single particle orbital with $\text{j =}\text{1}\text{2}$. We derive, within the framework of the Spin (6) symmetry, closed expressions for energies, electromagnetic (EO, M1, E2) transition rates, static moments and (one and two) nucleon transfer reaction intensities.     

Theory of optical spectra involving charge transfer states: dynamic localization predicts a temperature dependent optical band shift

The influence of charge transfer states on the optical line shape of chromophore complexes is investigated in a minimal model that includes a coupling between an excited state and an optically dark charge transfer state. In the calculations of the absorption spectrum, an intensity borrowing by the charge transfer state, strong vibrational sidebands, and a temperature dependent shift of optical transitions are obtained. The theory is applied to the bacterial photosynthetic reaction center to explain a 30 nm blueshift of the low-energy absorption band with increasing temperature.     

Near neutrality of an oxygen molecule adsorbed on a Pt(111) surface

The charge state of paramagnetic or nonmagnetic O2 adsorbed on a Pt(111) surface is analyzed using density functional theory. We find no significant charge transfer between Pt and the two adsorbed molecular precursors, suggesting these oxygen reduction reaction (ORR) intermediates are nearly neutral, and changes in magnetic moment come from self adjustment of O2 spin-orbital occupations. Our findings support a greatly simplified model of electrocatalyzed ORR, and also point to more subtle pictures of adsorbates or impurities interacting with crystal than literal integer charge transfers.     

Graded constraint algebras,OSP(1, 1|2) and superstring theory

Earlier, we have established that, for a constrained system with a first class bosonic constraint algebra, the standard BRST invariance generalizes to an OSP(1, 1|2) symmetry, with four nilpotent and anticommuting BRST-type operators. Here we generalize this to arbitrary constrained systems with a graded first class constraint algebra. Our approach is based on the Fradkin- Vilkovisky formalism and uses a relation between abelian and nonabelian constraint algebras. Subsidiary constraints and generalized structure constants play an important role in the construction. As an application, we construct the OSP(1, 1|2) generators for superstrings. Here the subsidiary constraints are identified with physically relevant operators used in the unitarity proof.     

Impurity scattering,Friedel oscillations and RKKY interaction in graphene

We investigate Friedel Oscillations (FO) surrounding a point scatterer in graphene. We find that the long-distance decay of FO depends on the symmetry of the scatterer. In particular, the FO of the charge density around a Coulomb impurity show a faster, δρ∼1/ r³, decay than in conventional 2D electron systems. In contrast, the FO of the exchange field which surrounds atomically sharp defects breaking the hexagonal symmetry of the honeycomb lattice decay according to the 1/r² law. We discuss the consequences of these findings for the temperature dependence of the resistivity of the material and the RKKY interaction between magnetic impurities.     

MMgF4:Eu(M=Ca,Sr,Ba)体系中铕离子的发光中心及价态

合成了铕离子激活的MMgF4.磷光体,研究了Eu3+离子的光谱特征与基质化合物的关系,存在三类发光中心,讨论了基质组成对铕离子价态的影响.     

Quantisation of 2D- gravity with Weyl and area- preserving diffeomorphism invariances

The constraint structure of the induced 2D-gravity with the Weyl and area-preserving diffeomorphism invariances is analysed in the ADM formulation. It is found that when the area-preserving diffeomorphism constraints are kept, the usual conformal gauge does not exist, whereas there is the possibility to choose the so-called “quasi-light-cone” gauge, in which besides the area-preserving diffeomorphism invariance, the reduced Lagrangian also possesses the SL(2, R) residual symmetry. This observation indicates that the claimed correspondence between the SL(2, R) residual symmetry and the area-preserving diffeomorphism invariance in both regularisation approaches does not hold. The string-like approach is then applied to quantise this model, but a fictitious non-zero central charge in the Virasoro algebra appears. When a set of gauge-independent SL(2, R) current-like fields is introduced instead of the string-like variables, a consistent quantum theory is obtained, which means that the area-preserving diffeomorphism invariance can be maintained at the quantum level.     

Fluctuation-facilitated charge migration along DNA

We propose a model Hamiltonian for charge transfer along the DNA double helix with temperature-driven fluctuations in the base pair positions acting as the rate limiting factor for charge transfer between neighboring base pairs. We compare the predictions of the model with the recent work of Barton and Zewail on the unusual two-stage charge transfer of DNA.