Quantum theory of post-collision interaction in inner-shell photoionization

We have performed fully quantum-mechanical and relativistic calculations of the post-collision-interaction effect in x-ray-induced argonK?L ₂ L ₃(¹ D) Auger and xenonL ₂?L ₃ N ₄(J=3) Coster-Kronig-electron emission. The Dirac-Fock computations include a complete integration over intermediate one-hole continuum states in the lowest-order expression of the resonant double-photoionization cross section. The results are in excellent agreement with synchrotron-radiation measurements of the post-collision-interaction shifts. We have also made nonrelativistic Hartree-Fock test calculations of the argonK?L ₂ L ₃(¹ D) and xenonL ₃?M ₄ M ₅(¹ G ₄) Auger-electron line shapes. The quantum-mechanical results are compared with rigorous semiclassical calculations which have been made without using the stationary-phase approximation. The results of this computational analysis are interpreted in terms of an analytical line-shape formula based on asymptotic Coulomb wave functions. As a consequence the most salient features of the post-collision interaction in inner-shell photoionization are explained.     

Angular dependent photoelectron spectral measurements for acetylene

The photoelectron angular distributions of acetylene have been obtained using 584 Å light. The π asymmetry parameter β of the CC triple bond is lower by 0.2 than the corresponding parameter of the CC double bond in ethylene. The β values of the π ionization and the second σ ionization are very close to each other indicating that the rule that π ionizations exhibit significantly higher β values than σ iomzations in unsaturated hydrocarbons is of limited utility here.     

Quantum-mechanical analogies for classical post-collision interaction effects in (e, 2e) collisions

A method is proposed for approximately computing the post collisional interaction of the two escaping electrons in otherwise standard first order ionisation calculations. At intermediate energies and in asymmetric kinematics the effects are found to be very small. The interactions of these electrons with the residual ion are considered through the use of distorted waves. For the slow one the latter are used in the calculations but for the fast one their effect is investigated using Fourier transforms. These interactions play a significant role.     

High resolution studies of deep core level threshold auger processes

The emission of Auger electrons associated with the photon induced threshold creation of an atomic inner-shell hole is a complex dynamical process. Detailed studies of this resonance phenomenon become possible through the combination of high-flux synchrotron radiation and state-of-the-art experimental techniques. We present experimental results for the resonantly excited L₃-M_4,5M_4,5 transition in Pd and Ag. While far above threshold the Auger lines are largely independent of the exciting photons, the emitted electron distribution undergoes drastic changes in the threshold region. The observations are discussed in terms of radiationless resonant inelastic scattering.     

Frequency dependent energy transfer in particle-field interaction

Dynamics of a particle in the plane electromagnetic wave is investigated by classical theory. By introducing the uncertainty principle into classical theory it is possible to explain the frequency dependent energy transfer in this interaction. Comparison with quantum theory is made and a very good agreement is found in almost all cases. Classical theory fails to describe a resonant process which occurs at a particular frequency of the electromagnetic plane wave.     

Distance dependent coherence variation in DNA charge-transfer processes

We explore distance dependent variation of the coherence length relevant to DNA charge-transfer processes within 5'-GAnG3-3' DNA sequences. Recently developed on-the-fly filtered propagator functional path integral approach was employed to sort out transport trajectories with significant contribution and to analyze correlation between electronic states. In particular, the coherence length was quantitatively determined through characteristics of off-diagonal quantum trajectories. Simulated coherence lengths and experimentally observed rate constants [Nature 2001, 412, 318] were found to be consistent such that, up to n = 2, the exponential decrease of the rate constants is associated with the donor-acceptor coherence driven charge transfer. In contrast, the rate constants become insensitive to the distance for n > or = 3 in which donor and acceptor are no longer significantly correlated. It was also found that the coherence within a collective state governs the overall charge transfer, which is composed of a part of a sequence within the coherence length from the donor.     

Angular and frequency dependent spin relaxation study of liquid crystalline cyanobiphenyls

NMR field-cycling measurements of the Larmor frequency (v) and angular (Δ) dependences of the longitudinal proton spin relaxation time T₁ for the nematic liquid crystals 5CB and 8CB allow a more detailed analysis of the underlying molecular motions than data available previously. All T₁ (v, Δ) dispersion profiles essentially distinguish three frequency ranges where T₁ is governed by either local field effects, collective motions (director order fluctuations), or rotational and translational diffusion of individual molecules or molecular groups, respectively. The angular dependence supports and extends previous conclusions about the significance of the order fluctuation term at low (kHz) and high (MHz) Larmor frequencies; in addition it is the basis for the disentanglement of local field effects, which involve Jeener's dipolar relaxation, and of the sophisticated rotational relaxation models suggested in the literature by Dong, Nordio and Vold. It is found that Vold's third rate concept gives the best explanation of the measurements. The results on the rotational diffusion processes essentially agree with deuteron studies from the literature, but also reveal clear distinctions with regard to the anisotropy parameter σ, essentially due to the improved separation from the order fluctuation contribution.     

Localized states in molecular auger spectra

The influence of the degree of localization of the two final holes on the Auger spectra of a simple diatomic molecule is analysed in detail and cases where such effects may be observed experimentally are discussed. The results are compared with studies of the valence band Auger spectra of solids.     

Anomalous auger shifts in chemisorption on tungsten

Substrate Auger line energy shifts for monolayer gas adsorption are readily detected. The observed shifts in tungsten are incompatible with predicted chemical-shift trends and hence relaxation effects must be considered. It is proposed that transition-metal s electrons play a decisive role in core-hole screening. The measurement of substrate Auger line energy shifts on gas adsorption may thus provide information on the contribution of these electrons to chemisorption.     

Angular photon-electron correlations induced by the weak interaction of neutral currents in light muonic atoms

The weak interaction of neutral currents of the negative muon and a nucleus leads to observableP-odd correlations in the one-photon 2s → 1s transition of light muonic atoms. Recently the author has been analyzed how these correlations are affected by the mixing of the 2p1/2 and 2p3/2 orbits induced by the hyperfine muonnucleus interaction.P-odd terms in an angular distribution and circular polarization of photons have been considered as an example. The above mixing proved to be significant in muonic beryllium and boron. The present work continues this analysis. The effect of the mixing onP-odd terms of angular correlations between momenta of the photon radiated in the 2s → 1s transition and a hard electron emitted in the μ-decay at the 1s orbit is studied here. This effect is found to be also significant. Moreover, the possibility of using the magnetic spin rotation to observe the angular correlations is discussed. A special experimental geometry is suggested. Its use allows uncertainties resulting from the absence of data on the orientation of the angular μ-atom momentum in the 2s state to be minimized.     

Role of electrostatic interaction in the processes of complex formation

Aspects of the theory of associate mixtures formed as a result of electrostatic interaction between their components are discussed. We obtained equations, convenient for comparison with the experiment, that elucidate the dependence of the association constant on the dielectric susceptibility of the solvent. The experimental results of the associates studied, which were composed of a diazo-salt cation and an anion of a xanthene dye, are described satisfactorily by the theoretical dependences, but with a smaller equilibrium distance between the associate component. We have shown that the smaller equilibrium distances are due to the fact that the dependence of the dielectric susceptibility of the solvent on the distance (r) for small distances between the interacting ions is not taken into account in the qualitative theory.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 5, pp. 591–596, September–October, 1986.     

Many-electron contributions in the auger spectrum of CO

The CO Auger electron spectrum has been re-investigated by means of ab initio MO LCAO calculations using a combined SCF CI procedure. The CI comprises internal and semi-internal contributions to the final double-hole Slate wave-functions. In particular, the latter contributions are found to be highly significant both with respect to energies and intensities of the Auger transitions. In order to compare with the experimental spectra, the intensities of the transitions have also been calculated using a simple one-center model.     

Time‐dependent density functional theory study on direction‐dependent electron and hole transfer processes in molecular systems

We report on real‐time time‐dependent density functional theory calculations on direction‐dependent electron and hole transfer processes in molecular systems. As a model system, we focus on α‐sulfur. It is shown that time scale of the electron transfer process from a negatively charged S₈ molecule to a neighboring neutral monomer is comparable to that of a strong infrared‐active molecular vibrations of the dimer with one negatively charged monomer. This results in a strong coupling between the electrons and the nuclei motion which eventually leads to S₈ ring opening before the electron transfer process is completed. The open‐ring structure is found to be stable. The similar infrared‐active peak in the case of hole transfer, however, is shown to be very weak and hence no significant scattering by the nuclei is possible. The presented approach to study the charge transfer processes in sulfur has direct applications in the increasingly growing research field of charge transport in molecular systems. © 2017 Wiley Periodicals, Inc.     

A new magic titanium-doped gold cluster and orientation dependent cluster-cluster interaction

The stability and structures of titanium-doped gold clusters Au(n)Ti (n=2-16) are studied by the relativistic all-electron density-functional calculations. The most stable structures for Au(n)Ti clusters with n=2-7 are found to be planar. A structural transition of Au(n)Ti clusters from two-dimensional to three-dimensional geometry occurs at n=8, while the Au(n)Ti (n=12-16) prefer a gold cage structure with Ti atom locating at the center. Binding energy and second-order energy differences indicate that the Au(14)Ti has a significantly higher stability than its neighbors. A high ionization potential, low electron affinity, and large energy gap being the typical characters of a magic cluster are found for the Au(14)Ti. For cluster-cluster interaction between magic transition-metal-doped gold clusters, calculations were performed for cluster dimers, in which the clusters have an icosahedral or nonicosahedral structure. It is concluded that both electronic shell effect and relative orientation of clusters are responsible for the cluster-cluster interaction.     

Angular dependent linewidths of ESR spin probes in oriented smectic systems. An application to oriented lecithin—cholesterol multibilayers

A theory, based on the diffusion model of molecular reorientation extended with an orienting potential, is developed for the angular dependence of the ESR linewidths of symmetrical top radicals in oriented smectic liquid crystals. The theoretical results have been compared with linewidth data obtained with the cholestane spin label in oriented multibilayers of equimolar quantities of dipalmitoyl lecithin and cholesterol. For the determiination of the linewidths, the ESR spectra were fitted to a line shape function, which includes unresolved proton hyperfine interactions.From the comparison of theory and experiment the rotational diffusion tensor and order parameter S can be found, giving D_⊥ = 3.4 × 10⁶ s^?1, D|/D_⊥ = 40 and S = 0.86 at 49°C. The high value of D|/D_⊥ indicates a strong anisotropic motion of the cholestane spin label. The order parameter found is in good agreement with the order parameter calculated from the angular dependence of the ESR line positions.     

Oligomethylene spacer length dependent interaction of synthetic galactolipids incorporated in phospholipid layers with ricin

As models of naturally occurring glycolipids, structurally well-determined amphiphilic compounds were prepared. The synthetic molecules have beta-d-galactopyranosyl or alpha-d-mannopyranosyl and two dodecyl groups as terminal hydrophilic sugar and hydrophobic hydrocarbon moieties, respectively. The two long alkyl chains are connected by 3,5-dioxybenzamide through ether linkages to give a lipid analog purified easily due to its absorbance of ultraviolet light. In the synthetic glycolipids, the glycoside and lipid parts are covalently bound via an oligomethylene spacer. The glycolipids could be easily incorporated into liposomes of l-alpha-phosphatidylcholine. The monoglycosyl moiety of the synthetic glycolipids possessing a hexamethylene spacer was present on the surface of the liposomes and interacted specifically with a lectin to give liposomal assemblies. Such agglutination of these liposomes induced by lectins was determined by analyses of turbidity and particle size based on dynamic light scattering and laser diffraction methods. The other liposomes possessing a shorter ethylene or longer decamethylene linker gave few lectin-induced agglutinates, indicating that these spacers were not effective for the presentation of the galacto-terminal on the liposomal surfaces. Similar spacer-dependent recognition of ricin with a galactolipid-incorporated phospholipid monolayer was confirmed by surface plasmon resonance technique on a substrate.     

Monitoring kinetic processes in polymer solutions with time dependent static light scattering (TDSLS)

An overview of recent developments in TDSLS and auxiliary techniques is given. This includes background theory, and examples of results and applications for online monitoring of polymerization reactions, kinetics and structural determinations from degrading polymers, aggregation, and dissolution of dry polymer powders. Also, automatic dilution techniques allow for continuous characterization of the equilibrium states of multi-component solutions. Illustrations are given for the case where the change in polyelectrolyte dimensions, interactions and hydrodynamics can be probed.     

Size dependent interaction of biofunctionalized CdS nanoparticles with tyrosine at different pH

Enhancement of fluorescence of CdS nanoparticles by tyrosine at pH 10 in contrast to Stern-Volmer quenching at pH 7 was observed and both the effects were found to depend on the size of the nanoparticles.