Possible anionic clusters and mixed valence effects in transition metal chalcogenides and oxides

The formation of anionic clusters similar to O₂^2?, S₂^2?, Se₂^2? but with higher internuclear distances can be responsible for the more specific forms of interaction required to explain the properties of UO₂₊x, and many transition metal chalcogenides such as Fe_1?xS, Ni_1?x,S etc. Resonant structures can lead to clusters of this type even in stoichiometric chalcogenides with NiAs-type structure due to the $\text{d}\text{p}$ mixing, and low energy differences between metal d- and chalcogen p-bands. The mixed valence effects involved are discussed qualitatively.     

Ramsey-CPT spectrum with the Faraday effect and its application to atomic clocks

A method that obtains the Ramsey-coherent population trapping(CPT) spectrum with the Faraday effect is investigated.An experiment is implemented to detect the light polarization components generated from the Faraday effect.The experimental results agree with the theoretical calculations based on the Liouville equation.By comparing with the method without using the Faraday effect,the potential of this method for a CPT-based atomic clock is assessed.The results indicate that this method should improve the short-term frequency stability by several times.     

Electron hopping in the Mössbauer spectrum of mixed valence freudenbergite

Samples of pure ferric, ferrous and mixed valence freudenbergite were prepared by different techniques. The ⁵⁷Fe Mössbauer spectra of the single valence samples showed poorly resolved quadrupole splittings for the ferric sample, two well-resolved quadrupole splittings for the ferrous sample and electron hopping at, and above, room temperature for the mixed valence sample, which disappeared on lowering the temperature to 50 K.     

Intermediate valence impurity with a local boson field. Response to external probes

The spinless Anderson impurity model accomplished by the coupling with local bosons is considered in the context of the response to external probes. The influence of the electron-boson coupling on the behaviour of the spectral functions is analysed with the help of the method of equations of motion for Green functions within the approximation scheme, leading to analytical expressions. With the increase of electron-boson coupling the boson satellite appears in the spectra whose structure is then smeared.     

Photoluminescence associated with impurity clusters in phosphorous doped silicon

Photoluminescence measurements as a function of excitation level and temperature are presented for Si(P) containing 7.5×10¹⁷ P atomd/cm³. The luminescence in Si(P) for intermediate concentrations in the range from 1×10¹⁶ to 2×10¹⁸ cm^?3 is interpreted in terms of recombination of trapped carriers at clusters of impurities.     

乙醚-水混合团簇的多光子电离质谱及从头算

应用多光子电离技术结合飞行时间质谱仪对乙醚与水的混合团簇进行了研究,实验中观测到了多个序列的质子化团簇： (CH3CH2OCH2CH3)nH+（n=1、2…6）、(CH3CH2OCH2CH3)nH2OH+（n=1、2…4）和(CH3CH2OCH2CH3)n(H2O)2H+ （n=2、3、4）。通过对质谱的研究发现,(CH3CH2OCH2CH3)3H2OH+为幻数结构。结合从头计算理论,在B3LYP/6-31G(d)基组水平上对乙醚与水混合团簇的可能构型进行优化,得到了其稳定构型。振动频谱分析显示,团簇中最强的红外振动模式主要来自氢键中H的伸缩振动的贡献。     

The interrelation between the Faraday effect and the inverse Faraday effect in a magnetic medium and the terahertz inverse Faraday effect in single molecule magnets

The interrelation between the Faraday and the inverse Faraday effects when the magneto-dipole interaction of a sample with an electromagnetic wave is essential has been phenomenologically investigated. This investigation was carried out in the spirit of well-known Pitaevsky’s approach. The terahertz inverse Faraday effect in single molecule magnets has been theoretically studied, the conditions favorable for observing this effect have been formulated.     

Low temperature properties of valence fluctuating cerium impurity with spin-orbit and crystal field splittings

The Anderson Hamiltonian, with spin-orbit and cubic crystal-field splittings, is studied using Brillouin-Wigner perturbation theory. The ratio between the low temperature paramagnetic susceptibility and the electronic specific heat coefficient is reported for both intermediate valent and Kondo regimes. We find that finite spin-orbit effect is not negligible in Ce systems in the intermediate valent regime. In the nearly integral valent case, for small Kondo temperatureT _K, we also find that even for relatively large crystalfield splitting (10T _K), if the free ion ground state is of ₇ symmetry, the effect of the ₈ level is still large.     

C/N/O centred metal clusters: super valence bonding and magic structure with 26 valence electrons

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al₆OM_m (M?=?Na, K; m?=?2,4,6) and a few other Al_nXNa_m (X?=?C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s²p⁶ shell closure, and the antibonding orbitals make the metal moieties form closed 2S²2P⁶ shells. The 26 valence electrons form closed s²p⁶S²P⁶D¹⁰ shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al₆O^2? core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals.     

Nonmagnetic impurity effects and neutron scattering spectrum in iron pnictides

We study the effect of local impurity and the neutron scattering spectrum based on the five-orbital model obtained by the first principle calculation for iron pnictides. We find that the interband impurity scattering is induced by the complex multiorbital structure. This fact means that the fully-gapped sign-reversing s-wave state, which is predicted by spin-fluctuation theories, is very fragile against impurities. The result suggests a reasonable possibility that the fully-gapped s-wave state without sign reversal (s₊₊-wave) would be realized in dirty iron pnictides. We also find that broad peak structure observed in the neutron scattering measurements can be explained by the s₊₊-wave state.     

Reciprocity of Faraday effect in ferrofluid: Comparison with magneto-optical glass

The transmission light intensity method is carried out on a classical platform to study the reciprocity of Faraday effect in water-based Fe₃O₄ ferrofluid and its diluents. Setting the polarization direction of the analyzer at an angle of 45° to that of the polarizer, the switchable DC magnetic field and the alternating magnetic field are imposed to ferrofluid. The ferrofluid film is replaced by magneto-optical glass for contrastive experiments. The results indicate that ferrofluid is different with magneto-optical glass. Even though the direction of magnetic field is reversed, the rotation direction of the polarized light does not change for ferrofluid. The theoretical model of magneto-optical rotation was used to describe the origin of the reciprocity of Faraday effect in ferrofluid and the non-reciprocity in magneto-optical glass. These findings suggest that the magnetic moments of nanoparticles in ferrofluid tend to the same orientation with the magnetic field because of the rotation of particles.     

Fano resonance in the impurity photoconductivity spectrum of InP doped with shallow donors

The Fano resonances in the impurity photoconductivity spectra of n-InP are investigated theoretically and experimentally. It is shown that the calculations describe the experimental data with an accuracy of up to 20%.     

The spinless periodic Anderson model with phonons and applications to mixed valence systems

A simplified periodic Anderson model, without spin and Hubbard correlation, coupled to a branch of optical phonons is presented and discussed in connection with Rare Earth compounds exhibiting a transition to a mixed valence state. The phonon self energy is approximately calculated by diagrammatic techniques and used for a study of boson modes originating from the interplay of phonons withf-electrons mixed into band states. It is shown that weakly damped low lying or even soft modes may exist in connection with the transition. The relevance of these results to real systems, possible shortcomings of the model and the relations to other work in this field is described.     

Model of interband pairing in mixed valence and heavy fermion systems

Various possible types of interband pairings in mixed valence and heavy fermion systems are investigated, using a two-band model with Kondo-type interaction. In this model, the system may develop interband singlet superconducting ordering, or electron-hole pairing of excitonic type, which induces an effectivef – d hybridization. The conditions for the realization of each of these orderings depends crucially on the dispersion of the corresponding original bands. The mutual influence of the two pairings, as well as the effect of external hybridization, are investigated.     

Bridge Effect in Charge Transfer Absorption Bands. Para-substituted Benzylideneacetones

Abstract

The electronic absorption charge transfer bands in a series of para - substituted benzalketones are analyzed in order to stablish the role of the electron-donor substkuent as well as the electronic properties of the molecular structure of the π-conduction channel.

Absorption bands assignment of the π-π^? electronic transitions in the near ultraviolet spectral region is carry out from an experimental and theoretical point of view. The photo-induced charge transfer spectral bands in these aromatic compounds follow the same spectral pattern than the para-substituted benzaldehydes and acetophenones and the electronic transition takes place in the π,π^?(¹L_a) excited state. However, our semiempirical M.O. calculations show that this charge transfer process involve the electron-acceptor carbonyl group and the olefinic bond bridge as a second electron-acceptor group.     

Ratchet effect in graphene with trigonal clusters

We introduce the Fisher information in the basis of decay modes of Markovian dynamics, arguing that it encodes important information about the behavior of nonequilibrium systems. In particular we generalize an orthonormality relation between decay eigenmodes of detailed balanced systems to normal generators that commute with their time-reversal. Viewing such modes as tangent vectors to the manifold of statistical distributions, we relate the result to the choice of a coordinate patch that makes the Fisher-Rao metric Euclidean at the steady distribution, realizing a sort of statistical equivalence principle. We then classify nonequilibrium systems according to their spectrum, showing that a degenerate Fisher matrix is the signature of the insurgence of a class of dynamical phase transitions between nonequilibrium regimes, characterized by level crossing and power-law decay in time of suitable order parameters. An important consequence is that normal systems cannot manifest critical behavior. Finally, we study the Fisher matrix of systems with time-scale separation.