Analysis of autoionizing Rydberg series Cu I 3d 9 4snl with the multichannel quantum defect theory

Using atomic beam technique, a combination of collisional and laser excitation, and photoion detection, autoionizing Cu I states in the region of the ionization limits Cu II 3d ⁹ 4s(^3,1 D) were investigated. In spite of the complicated structure of the signals due to the four different ionization limits³ D ₃,³ D ₂,³ D ₁ and¹ D ₂ and the large number of possible (LSJ)-states, which can be reached by this experimental technique, the majority of the signals could be attributed to definite Rydberg series 3d ⁹ 4s(³ D ₃,³ D ₂,³ D ₁,¹ D ₂)nl (LSJ). Perturbations were analyzed by the three- and four-channel quantum defect theory and by Hartree-Fock calculations. General formulas for the calculation of the photoionization cross section by the four-channel quantum defect theory in the case of two closed and two open channels are given.     

The diamagnetic Kepler problem

It has turned out that the analysis ofclassical periodic orbits is the key to understanding the modulations in thequantal spectra of hydrogen Rydberg atoms in magnetic fields. Inspired by this quantum chaological connection, we analyse some fundamental periodic orbits of the diamagnetic Kepler problem, abandoning the condition of vanishing azimuthal angular momentuml _z used in the literature so far. We report the bifurcation and confluence schemes of the orbits in their dependence onl _z and discuss the structural changes in terms of catastrophe theory.     

Ab initio study of MgH2: Destabilizing effects of selective substitutions by transition metals

The strong ionicity of H within rutile MgH₂ is reduced by selective substitution of Mg by T (=Fe, Co, Ni, Pd, Pt) using trirutile super-structure host TMg₂H₆. These novel model systems, as computed in the quantum mechanical framework of density functional theory, showed a gradual decrease of the charges carried by H down to −0.02e improving the use of MgH₂ for applications.     

Are there quantum beats from vacuum-induced coherence?

In a recent paper by Hegerfeldt and Plenio [1] it has been argued that for a certain class of V-level systems quantum beats could be observed even if the system was not in a coherent superposition of the upper levels. The beat frequency would be different to the upper level splitting. In their analysis, this was an effect of the quantum vacuum field which generated a coherent superposition of the upper levels in the course of the interaction. Their derivation is reanalyzed here using standard techniques which lead to a master-equation. Calculating the weak probe absorption spectrum, one finds that — as expected — the experimentally accessible, physical levels are the eigenstates of the combined system consisting of the atom and the vacuum which by definition do not couple. Thus, a coherent superposition will not be generated starting from a true, renormalized upper state and therefore quantum beating will only occur if an initial coherent superposition of renormalized upper levels is provided.This article was processed by the author using the LAT_EX style filepljour2 from Springer-Verlag.     

Quantum mechanical reactive scattering theory

In this article we briefly discuss a number of promising approaches to the formulation of a general, numerically exact, quantum mechanical theory of fully three-dimensional reactive atom-diatom collisions. It is noted that the ability to treat the three-dimensional H + H₂ exchange reactions is pre-requisite to any demonstration of the success of a general quantum mechanical formalism for reactivescattering. However, it is also noted that the time has come for any such theory to further demonstrate the ability to go beyond this basic, elementary atom-diatom exchange reaction. It is speculated that there now exist a number of approaches which can potentially provide such a general framework for quantum reactive scattering theory. Finally, a new generalizationof the Faddeev formalism for such systems, which is capable of inclusion ofthree body forces with a completely general form for the potential surface, is presented.     

Quantum mechanical study of the structure and stability of molecular van der Waals' clusters I: hydrates of SO2

The structure and stability of the mixed clusters SO₂(H₂O)_n, n ranging from 1 to 4, have been examined using semi-empirical quantum mechanical Hartree Fock methods with the improved PM3 parameter set as implemented in MOPAC [1]. Limited molecular dynamics studies together with investigation of the potential surface reveal potential barriers of 1 kcal/mol or less between many of the stable structures for a cluster of a given size. For n=1,2 the results are compared with those ofab initio calculations using a double zeta basis at the MP4 level.Supported in part by NSF Research Experience for Undergraduates     

Stochastic theory for molecular collisions in the perturbed stationary state formulation

The stochastic theory for molecular collisions is investigated within the framework of a perturbed stationary state formulation. In some cases we find it necessary to improve the theory by introducing a mixed quantum stochastic formulation. Three systems N₂0₂, and N₂OC are investigated and the results compared with exact quantum mechanical calculations.     

Isolated square planar metal complexes of carbon

Based on the group theory analysis and quantum chemical calculations within the framework of SW X _α method (in relativistic approximation for core electrons and non-relativistic for valence ones), the existence possibility of square planar complexes [M₄C] and [M₄C]^2? (M = Al, Ga, In, Tl, Sc, and Y) in gas phase has been shown. The extraction of Kt₂[M₄C] square planar complexes of carbon in the crystal state is possible too. A high stability of these complexes, in comparison with usual tetrahedral, is achieved due to the formation of five-and four-center bonds (bonds M-M and M-C).     

新型包覆数目可控的(CdTe/ZnS)nSiO2微球制备及细胞成像

以水相中快速合成的高质量核壳型CdTe/ZnS量子点为核,通过两步Stber法首次制备了硅壳包覆CdTe/ZnS数目可控的量子点微球(CdTe/ZnS)nSiO2,并完成氨基功能化修饰。通过紫外-可见分光光谱、红外光谱、荧光分光光谱、透射电子显微镜、粒度分析等相关方法对产物进行表征。结果证实:该合成方法不仅简便省时,易于放大生产,而且制备的氨基化微球具有52.1%的高荧光量子产率、稳定性强、生物相容性好。进一步将其用于标记Raw 264.7小鼠单核巨噬细胞和MCF-7人乳腺癌细胞,通过特征性膜成像表现膜电荷的分布,显示其在膜电荷对细胞行为的影响研究方面具有广阔的前景。     

Theory and spectroscopy of an incarcerated quantum rotor: The infrared spectroscopy,inelastic neutron scattering and nuclear magnetic resonance of H2@C60 at cryogenic temperature

The supramolecular complex, H₂@C₆₀, represents a model of a quantum rotor in a nearly spherical box. In providing a real example of a quantum particle entrapped in a small space, the system cuts to the heart of many important and fundamental quantum mechanical issues. This review compares the predictions of theory of the quantum behaviour of H₂ incarcerated in C₆₀ with the results of infrared spectroscopy, inelastic neutron scattering and nuclear magnetic resonance. For H₂@C₆₀, each of these methods supports the quantization of translational motion of H₂ and the coupling of the translational motion with rotational motion and provides insights to the factors leading to breaking of the degeneracies of states expected for a purely spherical potential. Infrared spectroscopy and inelastic neutron scattering experiments at cryogenic temperatures provide direct evidence of a profound quantum mechanical feature of H₂ predicted by Heisenberg based on the Pauli principle: the existence of two nuclear spin isomers, a nuclear spin singlet (para-H₂) and a nuclear triplet (ortho-H₂). Nuclear magnetic resonance is capable of probing the local lattice environment of H₂@C₆₀ through analysis of the H₂ motional effects on the ortho-H₂ spin dynamics (para-H₂, the nuclear singlet state, is NMR silent). In this review we will show how the information obtained by three different forms of spectroscopy join together with quantum theory to create a complementary and consistent picture which strikingly shows the intrinsically quantum nature of H₂@C₆₀.     

Local physical quantities for spin based on the relativistic quantum field theory in molecular systems

Local physical quantities for spin are investigated on the basis of the four‐ and two‐component relativistic quantum theory. In the quantum field theory, local physical quantities for spin such as the spin angular momentum density, spin torque density, zeta force density, and zeta potential play important roles in spin dynamics. We discuss how to calculate these local physical quantities based on the two‐component relativistic quantum theory. Some different types of relativistic numerical calculations of local physical quantities in Li atom and C₆H₆ are demonstrated and compared. Local physical quantities for each orbital are also discussed, and it is seen that a total local zeta potential is given as a result of some cancellation of large contributions from each orbital. © 2016 Wiley Periodicals, Inc.     

On the sudden approximation of cross: computational tests and factorization of cross sections and related scattering phenomena

A sudden approximation recently derived by Cross using a semiclassical treatment of the orbital motion is recast into a form which permits factorization of differential and integral degeneracy averaged cross sections, opacities as a function of final angular momentum quantum number, the scattering amplitude, and the phenomenological cross section which describes spectral line broadening. Calculations are done using an average of initial and final orbital angular momentum quantum numbers for the partial wave parameter for ArN₂, ArTIF, H⁺H₂ and Li⁺H₂. The results indicate that the method is a good approximation for integral cross sections and opacities when the energy sudden approximation is valid and when the coupling of the orbital motion is important.     

A quantum electronic theory of chemical processes—The inverted energy profile case: CH3+ + H2 reaction

A quantum approach to chemical processes is developed. The chemical interconversion is described as an electronic process. The reaction corresponds to histories involving quantum states belonging to different stationary molecular Hamiltonians. The system may be embedded in a weak (thermal) and/or external electromagnetic field. The electromagnetic transverse fields lead to transition moments yielding finite probability amplitudes for the system to change from one quantum state to another. Bottleneck subspaces (transition states) are defined; they mediate the interconversions in generic unimolecular and bimolecular processes. Active precursor and successor complexes are introduced to help bridge reactant and product electronic states. The stationary states are modeled with Born-Oppenheimer Hamiltonians. At a qualitative level, the theory is general. The rate, measured as a time derivative of product concentration, is expressed in terms of concentrations of active precursor and successor complexes. The kinetic coefficients are given in terms of quantum processes involving electronic bottleneck states. Stationary structures and vibrational zero-point energies characterizing the reactive CH₃++H₂ system are determined at a Hartree-Fock level of theory with 6-31++G** basis set. The vibrational levels are corrected with anharmonicity effects. The saddle point of index one for hydrogen scrambling reactions has been obtained and shown to be related to the CH₅⁺ molecular complex together with the precursor and successor complexes geometries. The unusual properties of the system with respect to standard transition-state theory are fairly well described within this approach, in particular, isotope scrambling as well as photon emission during formation of the carbocation. The theory suggests that these types of reactions, which are found in outer space, may contribute to the scattering of the cosmic microwave background. © 1997 John Wiley & Sons, Inc.     

A new formulation of the dynamical response of many-electron systems and the photoabsorption cross section of small metal clusters

Static polarizabilities and photoabsorption cross sections of clusters Na ₇ ^– , Na₈, Na ₁₉ ^– Na₂₀ are calculated, based on the spherical jellium model including the self-interaction correction (SIC) of Perdew and Zunger. To this end, a new formulation of the theory of the linear response is presented, which is suitable for general, self-interaction corrected, many-electron systems. The results obtained display an overall agreement with available experimental data, offering a systematic improvement with respect to the standard TDLDA. Furthermore, the cross sections of the negatively charged clusters are found to be dominated by a broad peak in the visible region, whose line width can be related to the lifetime of the surface plasmon against electron detachment.On leave of absence from the University of Coimbra, Portugal     

A Nuclear Singlet Lifetime of More than One Hour in Room‐Temperature Solution

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are supremely important techniques with numerous applications in almost all branches of science. However, until recently, NMR methodology was limited by the time constant T₁ for the decay of nuclear spin magnetization through contact with the thermal molecular environment. Long‐lived states, which are correlated quantum states of multiple nuclei, have decay time constants that may exceed T₁ by large factors. Here we demonstrate a nuclear long‐lived state comprising two ¹³C nuclei with a lifetime exceeding one hour in room‐temperature solution, which is around 50 times longer than T₁. This behavior is well‐predicted by a combination of quantum theory, molecular dynamics, and quantum chemistry. Such ultra‐long‐lived states are expected to be useful for the transport and application of nuclear hyperpolarization, which leads to NMR and MRI signals enhanced by up to five orders of magnitude.     

Trimethylaluminum: Bonding by Charge and Current Topology

The charge density distribution of the trimethylaluminum dimer was determined by high‐angle X‐ray diffraction of a single crystal and quantum‐chemical methods and analyzed using the quantum theory of atoms in molecules. The data can be interpreted as Al₂Me₆ being predominantly ionically bonded, with clear indications of topological asymmetry for the bridging Al? C bonds owing to delocalized multicenter bonding. This interpretation is supported by the calculated magnetic response currents. The data shed new light on the bonding situation in this basic organometallic molecule, which was previously described by contradicting interpretations of bonding.     

Energy transfer for systems possessing long-range rates of capture

The authors' recent theory of exciton trapping and sensitized luminescence is extended to cover long-range capture processes. Expressions are given for the energy transfer rate k_s, and the quantum yield ϕ_G, which show the interplay of exciton migration with the strength and range of the capture process.     

Discrete contributions to static dipole polarizabilities of excited bound states of non-relativistic hydrogen-like atoms

The static dipole polarizability α _{d, i} for an arbitrary bound state i of the non-relativistic hydrogen-like atom has been known for a long time from, e.g; the second-order perturbation theory treatment of the Stark effect. A reliable result for the ground state requires both summation over the discrete spectrum and inclusion of the continuum contribution. This continuum contribution is known to decrease for excited states, but a systematic study of this decrease has not been available so far. We present here representative results from a systematic study of α _{d, i} , which was performed as a first test of a new algorithm for the radial integrals involved. Partial sum approximations of the discrete contribution yield the total α _{d, i} with a relative error of less than 1% for all states i with principal quantum number n≥5. Corresponding results for the relativistic case, for which the radial integral algorithm was developed, will be presented elsewhere. Dedicated to Professor Hermann Stoll on the occasion of his 60th birthday An erratum to this article is available at .