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The study of chemical reactions in environments under nonequilibrium conditions has been of interest recently in a variety of contexts, including current-induced reactions in molecular junctions and scanning tunneling microscopy experiments. In this work, we outline a fully quantum mechanical, numerically exact approach to describe chemical reaction rates in such nonequilibrium situations. The approach is based on an extension of the flux correlation function formalism to nonequilibrium conditions and uses a mixed real and imaginary time hierarchical equations of motion approach for the calculation of rate constants. As a specific example, we investigate current-induced intramolecular proton transfer reactions in a molecular junction for different applied bias voltages and molecule–lead coupling strengths. [ABSTRACT FROM AUTHOR]

Understanding current-induced bond rupture in single-molecule junctions is both of fundamental interest and a prerequisite for the design of molecular junctions, which are stable at higher-bias voltages. In this work, we use a fully quantum mechanical method based on the hierarchical quantum master equation approach to analyze the dissociation mechanisms in molecular junctions. Considering a wide range of transport regimes, from off-resonant to resonant, non-adiabatic to adiabatic transport, and weak to strong vibronic coupling, our systematic study identifies three dissociation mechanisms. In the weak and intermediate vibronic coupling regime, the dominant dissociation mechanism is stepwise vibrational ladder climbing. For strong vibronic coupling, dissociation is induced via multi-quantum vibrational excitations triggered either by a single electronic transition at high bias voltages or by multiple electronic transitions at low biases. Furthermore, the influence of vibrational relaxation on the dissociation dynamics is analyzed and strategies for improving the stability of molecular junctions are discussed. [ABSTRACT FROM AUTHOR]

Chemistry students in Israel have two options for studying chemistry: basic or honors (advanced placement). For instruction in high school honors chemistry courses, we developed a module focusing on abstract topics in quantum mechanics: Chemistry--From the Nanoscale to Microelectronics. The module adopts a visual-conceptual approach, which replaces mathematical derivations and includes interdisciplinary, real-life applications. The module has also been used as enrichment material for an undergraduate mathematically oriented quantum chemistry course. We assessed the comprehension of quantum mechanical concepts and the thinking skills of high school honors students and undergraduate chemistry students who studied this module. These skills included visual and textual chemical understanding, graphing, and far transfer of learning. Participants included over 100 high school honors students in high and intermediate levels, and over 60 undergraduate students, with students separated into groups of those exposed to the module and those who received mathematics enrichment instead. The questionnaires revealed that both high school honors students and undergraduate students improved their scores. High-level academic students outperformed their undergraduate peers, and undergraduate students who had been exposed to the module outperformed undergraduates who had studied the topic with mathematical enrichment. The research contributes to the field of teaching quantum mechanics and thinking skills, suggesting that high school honors students and undergraduate students could benefit from studying quantum mechanics using a visual-conceptual approach along with real-life applications. This contribution is part of a special issue on teaching introductory chemistry in the context of the advanced placement (AP) chemistry course redesign.

Most undergraduate chemistry courses and a few high school honors courses, which focus on physical chemistry and quantum mechanics, are highly mathematically-oriented. At the Technion, Israel Institute of Technology, we developed a new module for high school students, titled "Chemistry--From 'the Hole' to 'the Whole': From the Nanoscale to Microelectronics." The module is based on a qualitative approach to teaching quantum chemistry, emphasizing interdisciplinary real-life applications and integration of visualization. While aimed at honors high school chemistry students, the module was also partially implemented and assessed in an undergraduate chemistry course. The research objective was to investigate the effect of the module on the visual and textual understanding of quantum mechanical concepts among 122 honors and 65 volunteer undergraduate chemistry students. The research tools included students' pre- and post-questionnaires. High school honors and undergraduate students, who were exposed to the module, significantly improved their textual and visual understanding of quantum mechanical concepts and their ability to move across illustrations and explanations. Honors and undergraduate students minimized the gap that had existed between them in terms of integrating micro and quantum levels into their post-questionnaire answers. Our findings augment the current set of the four chemistry understanding levels--macro, micro, symbol and process--by adding the quantum mechanical level as a fifth level of chemistry understanding. The study contributes to teaching physical chemistry by providing a tool for learning, assessment, and research of chemistry understanding via both visual and textual modes.

Quantum furling and unfurling are inelastic transitions between localized and delocalized electronic states. We predict scenarios where these processes govern charge transport through donor-bridge-acceptor molecular junctions. Like in the case of ballistic transport, the resulting currents are nearly independent of the molecular bridge length. However, currents involving quantum furling and unfurling processes can be controlled by the coupling to vibrations in the intra-molecular and the extra-molecular environment, which can be experimentally tuned. Our study is based on rate equations for exchange of energy (bosons) and particles (fermions) between the molecular bridge and its environment. An efficient algorithm is introduced for a compact representation of the relevant rate equations, which utilizes the redundancies in the rate matrix and the sparsity of the creation and annihilation operators in the molecular Fock space. [ABSTRACT FROM AUTHOR]

We explore the transport of fermions through a quantum conductor in the presence of contact vibrations. The latter are coupled to charge transfer between the fermion reservoirs and the conductor but remain inert to the charging state of the conductor itself. We derive explicit expressions for charge transfer rates into and out of the conductor which extend the scope of rate theories of inelastic transport to the presence of contact vibrations. Implementing the theory to a simple model with a uniform vibronic coupling at different contact orbitals, we demonstrate and analyze the effect of such vibrations on the charge current. Asymmetry between contact vibrations at the two reservoirs is shown to induce a pronounced current rectification, especially in the limit of floppy (low frequencies) contacts. At high frequencies, vibrational quantization is shown to suppress the effect, in accord with the increasing contact rigidity. This quantum result requires corrections beyond the classical theory of charge hopping. [ABSTRACT FROM AUTHOR]

It has been known for several decades that the electric current through tunneling junctions is affected by irradiation. In particular, photon-assisted currents by asymmetric irradiation of the two leads was demonstrated and studied extensively in tunneling junctions of different compositions and for different radiation wavelengths. In this work, this phenomenon is revisited in the context of single molecule junctions. Restricting the theoretical discussion to adiabatic periodic driving of one lead with respect to the other within a non-interacting electron formulation, the main features of specific molecules are encoded in the discrete electronic energy levels. The detailed level structure of the molecule is shown to yield new effects in the presence of asymmetric driving of the leads. In particular, when the field-free tunneling process is dominated by a single electronic level, the electric current can be suppressed to zero or flow against the direction of an applied static bias. In the presence of a second electronic level, a directional photo-electric effect is predicted, where not only the magnitude but also the direction of the steady state electric current through the tunneling junction can be changed by a monotonous increase of the field intensity. These effects are analyzed and explained by outlying the relevant theory, using analytic expressions in the wide-band limit, as well as numerical simulations beyond this limit. [ABSTRACT FROM AUTHOR]

The enolpyridine, OH-ketoenamime, NH equilibrium in crystals of 1,3-bis(pyridin-2-yl)propan-2-one is studied using temperature-dependent single-crystal x-ray diffraction. The report states that the theoretical model suggest the appearance of concerted hydrogen motions, which are unique to the dimer and can be used to quantify the effect of the supramolecular interaction on the hydrogen population in the crystal.

A new numerical method is introduced for the solution of Poisson's equation for the electrostatic potential between arbitrarily shaped boundary surfaces that may appear in the metal-molecule-metal junctions. This method is based on a straightforward procedure in which the arbitrarily shaped system is embedded in a cubic box.

Biological electron transfer (ET) is one of the most studied biochemical processes due to its immense importance in biology. For many years, biological ET was explained using the classical incoherent transport mechanism, i.e. sequential hopping. One of the relatively recent major observations in this field is long-range extracellular ET (EET), where some bacteria were shown to mediate electrons for extremely long distances on the micrometer length scales across individual nanowires. This fascinating finding has resulted in several suggested mechanisms that might explain this intriguing EET. More recently, the structure of a conductive G. sulfurreducens nanowire has been solved, which showed a highly ordered quasi-1D wire of a hexaheme cytochrome protein, named OmcS. Based on this new structure, we suggest here several electron diffusion models for EET, involving either purely hopping or several degrees of mixed hopping and coherent transport, in which the coherent part is due to a local rigidification of the protein structure, associated with a decrease in the local reorganization energy. The effect is demonstrated for two closely packed heme sites as well as for longer chains containing up to several dozens porphyrins. We show that the pure hopping model probably cannot explain the reported conductivity values of the G. sulfurreducens nanowire using conventional values of reorganization energy and electronic coupling. On the other hand, we show that for a wide range of the latter energy values, the mixed hopping-coherent model results in superior electron diffusion compared to the pure hopping model, and especially for long-range coherent transport, involving multiple porphyrin sites. [ABSTRACT FROM AUTHOR]

Within a generic model, we discuss the possibility of coherent control of charge fluxes in unbiased molecular junctions. The control is induced by resonances between the Rabi frequency due to a pumping laser field and internal characteristic frequencies of pre-designed molecular donor-bridge-acceptor complexes. Two models are considered: a coherently controlled molecular charge pump and a molecular switch. The study generalizes previous consideration of light induced current [M. Galperin and A. Nitzan, Phys. Rev. Lett. 95, 206802 (2005)] and of a molecular electron pump [R. Volkovich and U. Peskin, Phys. Rev. B 83, 033403 (2011)] and accounts for the coherently driven charge transport in an unbiased molecular junction with symmetric coupling to leads. Numerical examples demonstrate the feasibility of the control mechanism for realistic junctions parameters. [ABSTRACT FROM AUTHOR]

In a nanoscale molecular junction at finite bias voltage, the intramolecular distribution of vibrational energy can strongly deviate from the thermal equilibrium distribution and specific vibrational modes can be selectively excited in a controllable way, regardless of the corresponding mode frequency. This is demonstrated for generic models of asymmetric molecular junctions with localized electronic states, employing a master equation as well as a nonequilibrium Green’s function approach. It is shown that the applied bias voltage controls the excitation of specific vibrational modes by tuning the efficiency of vibrational cooling processes due to energy exchange with the leads. [ABSTRACT FROM AUTHOR]

A quantum sampling algorithm for the interpolation of diabatic potential energy matrices by the Grow method is introduced. The new procedure benefits from penetration of the wave packet into classically forbidden regions, and the accurate quantum mechanical description of nonadiabatic transitions. The increased complexity associated with running quantum dynamics is reduced by using approximate low order expansions of the nuclear wave function within a Multi-configuration time-dependent Hartree scheme during the Grow process. The sampling algorithm is formulated and applied for three representative test cases, demonstrating the recovery of analytic potentials by the interpolated ones, and the convergence of a dynamic observable. [ABSTRACT FROM AUTHOR]

Defining the conditions for coherent site-directed transport from an electron donor to a specific acceptor through tunneling barriers in a network of multiple donor/acceptors sites is an important step toward controlling electronic processes in molecular networks. The required analysis is most challenging since the entire network in essentially involved in coherent transport. In this work we introduce an efficient approach for formulating an effective donor/acceptor coupling in terms of the entire network parameters. The approach is based on implementation of Feshbach projection operators to map the entire network Hamiltonian onto a subspace defined by two specific donor and acceptor sites. This nonperturbative approach enables to define regimes of network parameters in which the effective donor-acceptor coupling is optimal. This is demonstrated numerically for simple models of molecular networks. [ABSTRACT FROM AUTHOR]

Possible mechanisms for charge-transport-induced dissociation in donor-bridge-acceptor complexes are studied. Two mechanisms for dissociation at the molecular bridge are captured within a simple model of an anharmonic bridge vibration coupled nonlinearly to an electronic degree of freedom. A direct mechanism is associated with vibronic excitations to the nuclear continuum and an alternative dissociation mechanism involves intermediate quasibound vibrational states (Feshbach resonances). The two different mechanisms of charge-transport-induced dissociation are analyzed and their interplay as a function of the system parameters is examined. A parameter regime is suggested where the phenomenon should be experimentally accessible. [ABSTRACT FROM AUTHOR]

The ability to control electronic tunneling in complex molecular networks of multiple donor/acceptor sites is studied theoretically. Our past analysis, demonstrating the phenomenon of site-directed transport, was limited to the coherent tunneling regime. In this work we consider electronic coupling to a dissipative molecular environment including the effect of decoherence. The nuclear modes are classified into two categories. The first kind corresponds to the internal molecular modes, which are coupled to the electronic propagation along the molecular bridges. The second kind corresponds to the external solvent modes, which are coupled to the electronic transport between different segments of the molecular network. The electronic dynamics is simulated within the effective single electron picture in the framework of the tight binding approximation. The nuclear degrees of freedom are represented as harmonic modes and the electronic-nuclear coupling is treated within the time-dependent Redfield approximation. Our results demonstrate that site-directed tunneling prevails in the presence of dissipation, provided that the decoherence time is longer than the time period for tunneling oscillations (e.g., at low temperatures). Moreover, it is demonstrated that the strength of electronic coupling to the external nuclear modes (the solvent reorganization energy) controls the coherent intramolecular tunneling dynamics at short times and may be utilized for the experimental control of site-directed tunneling in a complex network. [ABSTRACT FROM AUTHOR]

The Landauer-type formulation of current through a molecular junction with electronic-nuclear coupling introduced by Troisi et al. [J. Chem. Phys. 118, 6072 (2003)] is generalized to account for the dependence of the molecule-leads coupling terms on the nuclear coordinates. Although this electronic-nuclear coupling is external to the molecule there is no need to extend the molecular subspace when projection operators are employed for calculations of the current through the junction. A test case of a conductor with vibrating contacts to the leads is studied numerically. It is demonstrated that contact vibrations lead to inelastic contributions to the current and to characteristic features in the I-V curve and its derivatives, similar to the ones observed for internal (molecular) electronic-nuclear coupling. [ABSTRACT FROM AUTHOR]

A model for electron transfer in donor-bridge-acceptor complexes with electronic coupling to nuclear bridge modes is studied using the Redfield formulation. We demonstrate that the transport mechanism through the molecular bridge is controlled by the location of the electronic-nuclear coupling term along the bridge. As the electronic-nuclear coupling term is shifted from the donor/acceptor-bridge contact sites into the bridge, the mechanism changes from kinetic transport (incoherent, thermally activated, and bridge-length independent) to coherent tunneling oscillations. This study joins earlier works aiming to explore the factors which control the mechanism of electronic transport through molecular bridges and molecular wires. [ABSTRACT FROM AUTHOR]

The effect of electronic-nuclear coupling on electronic transport through a complex molecular network is studied. Electronic tunneling dynamics in a network of N donor/acceptor sites, connected by molecular bridges, is shown to be controlled by electronic-nuclear coupling at the bridges. Particularly, electronic coupling to an accepting nuclear mode at the contact site between the donor and the rest of the network is shown to affect the tunneling path selection to specific acceptors. In the “deep” tunneling regime, the network is mapped onto an N-level system using a recursive perturbation expansion, enabling analytical treatment of the electronic dynamics. The analytic formulation is applied for two model systems, demonstrating site-directed tunneling by electronic-nuclear coupling. Numerical simulations suggest that this phenomenon is not limited to the deep tunneling regime. [ABSTRACT FROM AUTHOR]

Effects of anharmonic bridge vibrations on electronic tunneling in donor-bridge-acceptor complexes are studied using a model of anharmonic bridge vibration coupled nonlinearly to an electronic degree of freedom. An anharmonicity parameter is introduced, enabling to reproduce the standard harmonic model with linear coupling as a limiting case. The frequency of electronic tunneling oscillations between the donor and acceptor sites is shown to be sensitive to the nuclear anharmonicity, where stretching and compression modes have an opposite effect on the electronic frequency. This phenomenon, that cannot be accounted for within the harmonic approximation, is analyzed and explained. [ABSTRACT FROM AUTHOR]

Electronic tunneling in a complex molecular network of N(>2) donor/acceptor sites, connected by molecular bridges, is analyzed. The “deep” tunneling dynamics is formulated using a recursive perturbation expansion, yielding a McConnell-type reduced N-level model Hamiltonian. Applications to models of molecular junctions demonstrate that the donor-bridge contact parameters can be tuned in order to control the tunneling dynamics and particularly to direct the tunneling pathway to either one of the various acceptors. [ABSTRACT FROM AUTHOR]

Deep electronic tunneling through molecular barriers in donor-bridge-acceptor complexes is studied using an analytically solvable model. The effective tunneling matrix element is formulated as a sum over vibronic tunneling pathways. For a symmetric system the frequency of tunneling oscillations is shown to increase with the strength of electronic-nuclear coupling at the bridge, the number of electronic-nuclear coupling sites, or the frequency of a bridge vibration. Acceleration by several orders of magnitude is demonstrated within the range of realistic molecular parameters. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the mechanism of electrons tunneling through a narrow water barrier between Pt(100) metal surfaces. Transmission probability for an incoming electron; Structural origin of the tunneling resonances; Time delay for the trapped electrons; Possible role played by structural cavities in the water structure.

Details the theoretical investigation of field induced switching in a disordered electron wave coupler. System in which quantum transport was demonstrated; Tunneling and its control in a 1D double well; Two-dimensional model for dual electron wave coupler with static defect.

We highlight a new manifestation of quantum interference in transport through single-molecule junctions, owing to different charge transport pathways from the molecule through the contacts into the three-dimensional electrode. Such contact interference can be identified with characteristic features of the current–voltage curve, as dramatic as closing an otherwise open transport channel. Based on analysis of the necessary conditions for observation of this phenomenon, we conclude that this effect should be detectable in relatively small molecules, where a molecular site shares coupling to two electrodes, and an electrode surface site shares coupling to different molecular sites. The importance of the surface-molecule connectivity scheme implies that commonly used reduced models which couple different molecular sites to effectively independent electrodes, fail to account for this effect and must be corrected in order to properly capture contact interference. [ABSTRACT FROM AUTHOR]

A numerical scheme is suggested for accurate large-scale quantum dynamics simulations. The time-dependent Schrödinger equation with finite time-dependent interaction terms is replaced by an inhomogeneous equation with imaginary boundary operators applied along the time axis. This equation is solved globally for a finite time interval using recent Krylov subspace-based iterative methods that are accelerated by a Fourier grid preconditioner. The same scheme is applied also to time-independent reactive-scattering calculations with absorbing boundary operators where the operation of the Green’s function is carried out by solving an inhomogeneous time-independent equation. The scheme is economic in terms of both memory requirement and computation time. It is especially favorable when high grid densities are required, e.g., for representation of highly oscillatory fields or high-energy wave functions. Illustrative applications are given for representative models of bound and dissociative systems driven by time-dependent pulsed fields, and for time-independent calculations of the cumulative reaction probability for the generic reaction H+H2 at high collision energies. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Final state-selected spectra in unimolecular decomposition are obtained by a random matrix version of Feshbach’s optical model. The number of final states which are independently coupled to the molecular quasibound states is identified with the number of states at the dividing surface of transition state theory (TST). The coupling of the transition state to the molecular complex is modeled via a universal random matrix effective Hamiltonian which is characterized by its resonance eigenstates and provides the correct average unimolecular decay rate. The transition from nonoverlapping resonances which are associated with isolated Lorentzian spectral peaks, to overlapping resonances, associated with more complex spectra, is characterized in terms of deviations from a χ2-like distribution of the resonance widths and the approach to a random phase-distribution of the resonance scattering amplitudes. The evolution of the system from a tight transition state to reaction products is treated explicitly as a scattering process where specific dynamics can be incorporated. Comparisons with recently measured final state-selected spectra and rotational distributions for the unimolecular reaction of NO2 show that the present model provides a useful new approach for understanding and interpreting experimental results which are dominated by overlapping resonances. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new approach is introduced for computing probabilities of molecular transitions in time-dependent fields. The method is based on the stationary (t,t’) representation of the Schrödinger equation and is shown to be equivalent to infinite order time-dependent perturbation theory. Bound-to-bound (i.e., photoexcitation) and bound-to-continuum (i.e., photoreaction) transitions are regarded as reactive collisions with the ‘‘time coordinate’’ as the reaction coordinate in an extended Hilbert space. A numerical method based on imposing absorbing boundary conditions for the time coordinate in a discrete variable representation framework is introduced. A single operation of the Green’s operator provides all the state-specific transition probabilities as well as partial state-resolved (inclusive) reaction probabilities. Illustrative numerical applications are given for model systems. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Unimolecular decay processes are studied in the regime of overlapping resonances with the goal of elucidating how unimolecular reaction rates depend on resonances widths (the imaginary part of the Siegert eigenvalues). As illustrated analytically for one-dimensional models and numerically for a more general random matrix version of Feshbach’s optical model, transition state theory (TST, Rice–Ramsperger–Kassel–Marcus) provides the correct average unimolecular decay rate whether the resonances are overlapping or not. For all studied cases, the explicit ‘‘universal’’ dependence of the TST average rate on the average resonance width (for a given energy, or an energy interval) is that of a saturation curve: in the regime of nonoverlapping resonances (i.e., weak coupling) the standard relation ‘‘unimolecular decay rate=resonance width /h’’ holds, but as the resonance overlap increases (strong coupling) the rate saturates, becoming practically independent of the average resonance width in the strong overlapping limit. On the basis of these conclusions, a discussion of what has been or can be measured in experiments of unimolecular decay that relates to the average decay rate and to the resonance widths is given. © 1994 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Using the (t,t’) method as introduced in Ref. [J. Chem. Phys. 99, 4590 (1993)] computational techniques which originally were developed for time independent Hamiltonians can be used for propagating an initial state for explicitly time dependent Hamiltonians. The present paper presents a time dependent integrator of the Schrödinger equation based on a Chebychev expansion, of the operator U(x,t’,t0→t), and the Fourier pseudospectral method for calculating spatial derivatives [(∂2/∂x2),(∂/∂t’)]. Illustrative numerical examples for harmonic and Morse oscillators interacting with CW and short pulsed laser fields are given. [ABSTRACT FROM AUTHOR]

A new approach is introduced for the calculation of multiphoton partial decay rates in ionizing and dissociative processes. The partial decay rates (partial resonance widths) are calculated by carrying out asymptotic analysis of a complex scaled resonance quasienergy solution of the time-dependent Schrödinger equation obtained when the acceleration, momentum, reduced momentum, or length gauges are used. The partial width analysis is made only after applying the proper complex-scaled transformations on the resonance solution. The recently developed (t,t’) algorithm [J. Chem. Phys. 99, 4590 (1990)] significantly reduces the computational effort when the Hamiltonian is represented in the momentum gauge or in the length gauge. The new approach is applied to a model Hamiltonian which describes the multiphoton detachment of Cl- in the ArF laser field. [ABSTRACT FROM AUTHOR]

A new powerful computational method is introduced for the solution of the time dependent Schrödinger equation with time-dependent Hamiltonians (not necessarily time-periodic). The method is based on the use of the Floquet-type operator in an extended Hilbert space, which was introduced by H. Sambe [Phys. Rev. A 7, 2203 (1973)] for time periodic Hamiltonians, and was extended by J. Howland [Math Ann. 207, 315 (1974)] for general time dependent Hamiltonians. The new proposed computational algorithm avoids the need to introduce the time ordering operator when the time-dependent Schrödinger equation is integrated. Therefore it enables one to obtain the solution of the time-dependent Schrödinger equation by using computational techniques that were originally developed for cases where the Hamiltonian is time independent. A time-independent expression for state-to-state transition probabilities is derived by using the analytical time dependence of the time evolution operator in the generalized Hilbert space. Illustrative numerical examples for complex scaled time periodic model Hamiltonians are given. [ABSTRACT FROM AUTHOR]

The complex coordinate scattering theory for the calculation of T-matrix elements, as was introduced by Engdahl, Moiseyev, and Maniv [J. Chem. Phys. 94, 1636 (1991)] and by Peskin and Moiseyev [J. Chem. Phys. 96, 2347 (1992)], is shown to satisfy the complex version of the Kohn variational principle introduced by Nuttall and Cohen [Phys. Rev. 188, 1542 (1969)]. This theory and the related S-matrix version of the Kohn variational principle, developed by Zhang, Chu, and Miller [J. Chem. Phys. 88, 6233, (1988)] are combined to formulate a generalized variational basis set approach for quantum scattering calculations. In this approach the Kohn variational procedure to optimize the linear parameters in the T matrix is followed by an optimization of the complex nonlinear parameters. This enables the application of the complex coordinate analytical continuation of the T matrix to the calculation of scattering probability amplitudes for long range potentials. Illustrating numerical applications to short and long range potentials are given. [ABSTRACT FROM AUTHOR]

The complex coordinate scattering theory is reformulated and applied to He/Cu(115) scattering. The weakly asymmetric corrugated surface leads to strong dependence of the diffraction intensities on the direction of the incident He beam. The calculated transition probabilities are in excellent agreement with the experimental values measured by Perreau and Lapujoulade. We show that additional information about the atom/surface interaction potential can be obtained if another experiment would be carried out when the Cu crystal will be rotated by 180°. [ABSTRACT FROM AUTHOR]

The method developed by Engdahl–Moiseyev–Maniv [J. Chem. Phys. 94, 1636 (1991)] for computing the scattering intensities of atomic beams from periodically corrugated solid surface is presented in more general form for scattering of molecules from solid surfaces. The method is numerically exact. By complex scaling of the Hamiltonian the full Green operator is calculated, using techniques that were originally developed for bound states. There is no need to impose specific boundary conditions on the scattering states. The method is used to calculate the rotationally inelastic transition intensities vs normal incident beam energy for HD scattering from Ag(111) and Pt(111) surfaces. Our results are in a very good agreement with theoretical scattering transition probabilities previously obtained by Whaley and Light and by Schinke. [ABSTRACT FROM AUTHOR]

Proposes the use of temperature-dependent Schrodinger equation for the study of quantum mechanical system-bath dynamics. Application of a time-dependent self consistent field (TDSCF) approximation for a system-bath wave function; Effects of TDSCF approximation; Analysis on the quantum mechanical system-bath correlations.

A brief review of the clock-based definition of the tunneling traversal time is presented. The applicability of the tunneling time concept to resonant tunneling processes, within a simple one-dimensional double barrier model, is discussed.