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Showing papers in "Annual Review of Physical Chemistry in 1999"


Journal ArticleDOI
TL;DR: This review is about understanding and controlling organic molecular adsorption on silicon and a discussion of recent studies of adsorbate structure is presented to provide a microscopic picture of structure and bonding in covalently attached molecule-silicon surface systems.
Abstract: This review is about understanding and controlling organic molecular adsorption on silicon. The goal is to provide a microscopic picture of structure and bonding in covalently attached molecule-silicon surface systems. The bias here is that an unprecedented, detailed understanding of adsorbate-surface structures is required in order to gain the control necessary to incorporate organic function into existing technologies or, eventually, to make new molecule-scale devices. A discussion of recent studies of adsorbate structure is presented. This includes simple alkenes, polyenes, benzene, and carene adsorbed on Si(100). Also included is a discussion of wet chemical procedures for forming alkyl and alkoxy covalently functionalized silicon. These discussions are presented together with comments on the related issues of adsorption dynamics and nano-scale manipulation in an effort to point the way toward principles and procedures that will allow the hybrid properties of organic molecules and surfaces to be harnessed.

573 citations


Journal ArticleDOI
TL;DR: Although polyatomic transition metal clusters cannot be characterized by the traditional methods of molecular spectroscopy, the combination of other physical and chemical probes can provide qualitative and semiquantitative structural information.
Abstract: Atoms and small molecules react with transition metal clusters in ways that are analogous to the physisorption and chemisorption reactions observed on the corresponding extended metal surface. However, often underlying these similarities are size-dependent variations in the reaction mechanisms and rates, the interpretation of which requires a detailed understanding of the structures of both the bare metal cluster substrates and the cluster-molecule complexes. Although polyatomic transition metal clusters cannot be characterized by the traditional methods of molecular spectroscopy, the combination of other physical and chemical probes can provide qualitative and semiquantitative structural information. These techniques, when combined with equilibrium geometries calculated using ab initio or semiempirical methods, provide a detailed picture of the structural origin of metal cluster reactivity and its variation with size.

271 citations


Journal ArticleDOI
TL;DR: This review focuses on time-dependent methods suitable for simulating the quantum dynamics of processes in large clusters and condensed-phase environments that avoid the conventional exponential scaling with the number of degrees of freedom.
Abstract: ▪ Abstract This review focuses on time-dependent methods suitable for simulating the quantum dynamics of processes in large clusters and condensed-phase environments. A number of mean field, quantum-classical, and quantum statistical approximations that avoid the conventional exponential scaling with the number of degrees of freedom are reviewed. In addition, rigorous semiclassical and path integral approaches are described that are feasible in certain physical situations. Select chemical applications illustrating the capabilities of these methods are discussed.

228 citations


Journal ArticleDOI
TL;DR: The article concludes with selected applications that highlight the strengths of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.
Abstract: ▪ Abstract The basic principles and recent advances in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry are reviewed. A brief history of electrospray ionization is provided, along with a complete technical description of the technique, electrospray ionization variations, and advantages. Next, the fundamental principles of Fourier transform ion cyclotron resonance mass spectrometry are covered, including ion cyclotron motion, ion cyclotron resonance excitation, and image current detection. Instrumentation and methods used to couple these techniques are then described. Topics include ion source configuration, ion transport through a strong magnetic field gradient, and ion trapping methods. The article concludes with selected applications that highlight the strengths of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

128 citations


Journal ArticleDOI
TL;DR: The vibrational spectrum of phosphaethyne, HCP, in its electronic ground state, as revealed by complementary experimental and theoretical examinations is discussed, which provides a detailed spectroscopic picture of the breaking of one bond and the formation of a new one.
Abstract: ▪ Abstract In this overview we discuss the vibrational spectrum of phosphaethyne, HCP, in its electronic ground state, as revealed by complementary experimental and theoretical examinations. The main focus is the evolution of specific spectral patterns from the bottom of the potential well up to excitation energies of approximately 25,000 cm−1, where large-amplitude, isomerization-type motion from H–CP to CP–H is prominent. Distinct structural and dynamical changes, caused by an abrupt transformation from essentially HC bonding to mainly PH bonding, set in around 13,000 cm−1. They reflect saddle-node bifurcations in the classical phase space—a phenomenon well known in the nonlinear dynamics literature—and result in characteristic patterns in the spectrum and the quantum-number dependence of the vibrational fine-structure constants. Two polar opposites are employed to elucidate the spectral patterns: the exact solution of the Schrodinger equation, using an accurate potential energy surface and an effective...

114 citations


Journal ArticleDOI
TL;DR: Methods for generating and detecting shock effects and several applications of shock spectroscopy are reviewed, including high explosives, the nanoshock technique that uses ultrafast lasers, and shock compression of biological molecules.
Abstract: ▪ Abstract Recent progress in combining the techniques of time-resolved molecular spectroscopy with shock compression science is reviewed. Shock wave spectroscopy probes the response of molecules to high-speed, large-amplitude mechanical transients and is an important way of studying physical chemical phenomena that involve large-amplitude displacements. A brief discussion of the continuum model for shock compression and a molecular model for the shock front is presented. Methods for generating and detecting shock effects are reviewed. Several applications of shock spectroscopy are reviewed, including high explosives, the nanoshock technique that uses ultrafast lasers, and shock compression of biological molecules.

113 citations


Journal ArticleDOI
TL;DR: The development of the basic models over the past 30 years has provided a useful means of investigating the nonadiabatic molecular dynamics and the idea of analytical continuation of classical dynamical variables into complex-valued phase space and time is emphasized.
Abstract: ▪ Abstract This chapter discusses the impact of two-state models of nonadiabatic coupling by Landau, Zener, Stuckelberg, Rosen, and Teller on the current theory of nonadiabatic interaction. In particular, the idea of analytical continuation of classical dynamical variables into complex-valued phase space and time is emphasized. The development of the basic models over the past 30 years has provided us with a useful means of investigating the nonadiabatic molecular dynamics; this is illustrated by the references to our earlier and most recent work.

104 citations


Journal ArticleDOI
TL;DR: This article reviews recent progress in understanding of gas-phase neutral reaction dynamics as made possible by improvements in the crossed molecular beam scattering technique for measuring reactive differential cross sections.
Abstract: ▪ Abstract This article reviews recent progress in our understanding of gas-phase neutral reaction dynamics as made possible by improvements in the crossed molecular beam scattering technique for measuring reactive differential cross sections. A selection of crossed-beam studies on systems that play a fundamental role in our basic understanding of reaction phenomena are discussed to illustrate the capabilities of the experimental method. The examples include benchmark atom-diatom abstraction and insertion reactions, and four-atom radical reactions for which state-to-state, state-resolved, or state-averaged differential cross sections have recently been measured. The results are discussed in the light of the latest related theoretical developments regarding the treatment of potential energy surfaces and the dynamics of the systems. Recent results on crossed-beam studies of chemically relevant reactions of carbon, nitrogen, and oxygen atoms are also reviewed, and the latest developments in the technique are...

100 citations


Journal ArticleDOI
TL;DR: This review provides a discussion of recent techniques for simulation of phase equilibria of complex fluids, and describes recent developments, such as the use of expanded-ensemble, tempering, or histogram reweighting techniques.
Abstract: ▪ Abstract This review provides a discussion of recent techniques for simulation of phase equilibria of complex fluids. Monte Carlo methods are emphasized over molecular dynamics methods. We describe recent developments, such as the use of expanded-ensemble, tempering, or histogram reweighting techniques. Our discussion of such developments is aimed at a general audience and is intended to provide an overview of the main advantages and limitations of each particular technique. References are provided to allow interested readers to identify and trace back most recent applications of a particular simulation technique. We conclude with general guidelines regarding selection of suitable simulation methods for particular problems and systems of interest.

90 citations


Journal ArticleDOI
TL;DR: This paper reviews recent developments in the field of nonlinear chemical kinetics and discusses new approaches to complex reaction mechanisms, stoichiometric network analysis, classification of chemical oscillators and formulation of their mechanisms by deduction from experiments, and correlation metric construction of reaction pathways from measurements.
Abstract: ▪ Abstract This paper reviews recent developments in the field of nonlinear chemical kinetics. Five topics are dealt with: (a) new approaches to complex reaction mechanisms, stoichiometric network analysis, classification of chemical oscillators and formulation of their mechanisms by deduction from experiments, and correlation metric construction of reaction pathways from measurements; (b) thermodynamic and stochastic theory of nonequilibrium processes, the eikonal approximation, the evaluation of stochastic potentials, experimental tests of the thermodynamic and stochastic theory of relative stability, and fluctuation-dissipation relations in nonequilibrium chemical systems; (c) chemical kinetics and cellular automata and lattice gas automata; (d) theoretical approaches and experimental studies of stochastic resonance in chemical kinetics; and (e) rate processes in disordered systems, stochastic Liouville equations, stretched exponential relaxation in disordered systems, and universality classes for rate...

75 citations


Journal ArticleDOI
TL;DR: Aspects of "impulsive stimulated scattering," when adapted to measurements in the diamond-anvil high-pressure cell, provide an approach to the determination of a subset of equilibrium and dynamic properties at high density.
Abstract: ▪ Abstract The elastic, thermodynamic, and transport properties of crystals and fluids at high temperature and pressure play a central role in the earth and planetary sciences as well as in a variety of technologies. These properties also constitute a principal experimental constraint on the description of intermolecular interactions at short distances. Aspects of “impulsive stimulated scattering,” when adapted to measurements in the diamond-anvil high-pressure cell, provide an approach to the determination of a subset of equilibrium and dynamic properties at high density.

Journal ArticleDOI
TL;DR: Technical progress in measuring fast and ultrafast photothermal phenomena is reviewed for solid-liquid interfaces, including colloidal solutions.
Abstract: ▪ Abstract Recent studies on fast (<10 ns) and ultrafast (<10 ps) photothermal and photoacoustic phenomena occurring at solid-liquid interfaces are discussed, including related topics, with emphasis placed on interfaces between aqueous solutions and metals under electrochemical potential control. Details of transient reflecting grating measurements for metal-liquid interfaces are considered as they relate to mesoscopic interface structures and nano-environments. Dependencies of fast photothermal phenomena on the electrochemical potential and types of anions in the solutions are shown. Ultrafast photothermal phenomena observed by transient reflectivity measurements are considered in connection with interface femtochemistry and hot electron reactions. Technical progress in measuring fast and ultrafast photothermal phenomena is reviewed for solid-liquid interfaces, including colloidal solutions.

Journal ArticleDOI
TL;DR: The way in which, in the Italy of the years immediately after World War II, interest in the dynamics of molecular processes was awakened is reviewed.
Abstract: ▪ Abstract This paper reviews the way in which, in the Italy of the years immediately after World War II, interest in the dynamics of molecular processes was awakened. The narrative begins with the work of a small number of chemists and physicists who, in the initial stage, interacted closely. In the course of the years, their interests diverged and younger people joined the newly formed groups. Even now, after half a century, a common approach can still to be seen regarding how to attack problems and perform experiments. Experimental work is discussed, bringing out the common viewpoint of fields as diverse as mass spectrometry, isotope effects, chemical kinetics, molecular beams, molecule-molecule interactions, molecule-ion interactions, molecule-surface interactions, and plasma chemistry.