Beyond Born Oppenheimer

INTRODUCING A POWERFUL APPROACH TO DEVELOPING RELIABLE QUANTUM MECHANICAL TREATMENTS OF A LARGE VARIETY OF PROCESSES IN MOLECULAR SYSTEMS. The Born-Oppenheimer approximation has been fundamental to calculation in molecular spectroscopy and molecular dynamics since the early days of quantum mechanics. This is despite well-established fact that it is often not valid due to conical intersections that give rise to strong nonadiabatic effects caused by singular nonadiabatic coupling terms (NACTs). In Beyond Born-Oppenheimer, Michael Baer, a leading authority on molecular scattering theory and electronic nonadiabatic processes, addresses this deficiency and introduces a rigorous approach--diabatization--for eliminating troublesome NACTs and deriving well-converged equations to treat the interactions within and between molecules. Concentrating on both the practical and theoretical aspects of electronic nonadiabatic transitions in molecules, Professor Baer uses a simple mathematical language to rigorously eliminate the singular NACTs and enable reliable calculations of spectroscopic and dynamical cross sections. He presents models of varying complexity to illustrate the validity of the theory and explores the significance of the study of NACTs and the relationship between molecular physics and other fields in physics, particularly electrodynamics. The first book of its king Beyond Born-Oppenheimer: * Presents a detailed mathematical framework to treat electronic NACTs and their conical intersections * Describes the Born-Oppenheimer treatment, including the concepts of adiabatic and diabatic frameworks * Introduces a field-theoretical approach to calculating NACTs, which offers an alternative to time-consuming ab initio procedures * Discusses various approximations for treating a large system of diabatic Schrödinger equations * Presents numerous exercises with solutions to further clarify the material being discussed Beyond Born-Oppenheimer is required reading for physicists, physical chemists, and all researchers involved in the quantum mechanical study of molecular systems.

This unique volume offers a clear perspective of the relevant methodology relating to the chemical theory of the next generation beyond the Born-Oppenheimer paradigm. It bridges the gap between cutting-edge technology of attosecond laser science and the theory of chemical reactivity. The essence of this book lies in the method of nonadiabatic electron wavepacket dynamic, which will set a new foundation for theoretical chemistry. In light of the great progress of molecular electronic structure theory (quantum chemistry), the authors show a new direction towards nonadiabatic electron dynamics, in which quantum wavepackets have been theoretically and experimentally revealed to bifurcate into pieces due to the strong kinematic interactions between electrons and nuclei. The applications range from nonadiabatic chemical reactions in photochemical dynamics to chemistry in densely quasi-degenerated electronic states that largely fluctuate through their mutual nonadiabatic couplings. The latter is termed as “chemistry without the potential energy surfaces” and thereby virtually no theoretical approach has been made yet. Restarting from such a novel foundation of theoretical chemistry, the authors cast new light even on the traditional chemical notions such as the Pauling resonance theory, proton transfer, singlet biradical reactions, and so on. Contents:The Aim of This Book: Where are We?Basic Framework of Theoretical ChemistryNuclear Dynamics on Adiabatic Electronic Potential Energy SurfacesBreakdown of the Born–Oppenheimer Approximation: Classic Theories of Nonadiabatic Transitions and Ideas BehindDirect Observation of the Wavepacket Bifurcation Due to Nonadiabatic TransitionsNonadiabatic Electron Wavepacket Dynamics in Path-branching RepresentationDynamical Electron Theory for Chemical ReactionsMolecular Electron Dynamics in Laser Fields Readership: Graduate students, professional scientists in theoretical chemistry, quantum chemistry, chemical dynamics, nonadiabatic transition, molecular physics, electron dynamics, and experimentalists in laser chemistry (including ultrafast chemical dynamics), photochemistry, laser control of chemical reactions, and scientists working in physical chemistry and chemical physics in general. Key Features:Presents a new framework of theory for ultrafast chemical reactions based on the nonadiabatic electron wavepacket dynamicsOffers a very powerful yet futuristic methodology to handle the attosecond electron-wavepacket quantum dynamics associated with non-Born-Oppenheimer nuclear pathsDescribes the original and powerful practices to cope with actual molecular systems that have been attained through authors' long-standing studiesKeywords:Electron Dynamics;Laser Chemistry;Nonadiabatic Transitions;Quantum Wave Packet;Ultrafast Chemical Dynamics;Attosecond Dynamics;Control Of Chemical Reactions;Photodynamics;Avoided Crossing;Conical Intersection;Pump-Probe;Photoelectron Spectroscopy;Excited State Chemistry;Semiclassical Theory

An introduction to the rapidly evolving methodology of electronic excited states For academic researchers, postdocs, graduate and undergraduate students, Quantum Chemistry and Dynamics of Excited States: Methods and Applications reports the most updated and accurate theoretical techniques to treat electronic excited states. From methods to deal with stationary calculations through time-dependent simulations of molecular systems, this book serves as a guide for beginners in the field and knowledge seekers alike. Taking into account the most recent theory developments and representative applications, it also covers the often-overlooked gap between theoretical and computational chemistry. An excellent reference for both researchers and students, Excited States provides essential knowledge on quantum chemistry, an in-depth overview of the latest developments, and theoretical techniques around the properties and nonadiabatic dynamics of chemical systems. Readers will learn: ● Essential theoretical techniques to describe the properties and dynamics of chemical systems ● Electronic Structure methods for stationary calculations ● Methods for electronic excited states from both a quantum chemical and time-dependent point of view ● A breakdown of the most recent developments in the past 30 years For those searching for a better understanding of excited states as they relate to chemistry, biochemistry, industrial chemistry, and beyond, Quantum Chemistry and Dynamics of Excited States provides a solid education in the necessary foundations and important theories of excited states in photochemistry and ultrafast phenomena.

Born-Oppenheimer (BO) theory and its treatment for solving molecular Schr]odinger Equation (SE), as proposed1 in 1927 and later on with Huang2 in 1954, has been the cornerstone of our understanding of chemical processes employing quantum chemistry. The triumph of BO treatment lies on the huge mass difference of electrons and nuclei allowing us to separate their motions while studying molecular quantum mechanics. The approximation allows us to study the electron dynamics which parametrically depends on the nuclear positions. In the limiting situation of such mass differences (me MN), the BO approximation could able to describe some of the chemical processes satisfactorily that mainly occur at lower energy regimes of ground electronic state. However, nature exhibits a whole range of molecular phenomena where we observe a violation of such a 'celebrated' approximation. These situations arise whenever electronic and nuclear motion gets coupled owing to different reasons that leads to what is known as nonadiabatic events. Simplest instances are photosynthesis, vision, charge transfer chemical reactions, solar energy conversion and photochemical reactions, all of which involve electronically excited states and thus, cannot be fully accounted for if considered solely from a BO per-spective. Owing to such range of nonadiabatic phenomena, failure of BO approximation is encountered quite often in nature rather than rarely.

Explicitly Correlated Wave Functions in Chemistry and Physics is the first book devoted entirely to explicitly correlated wave functions and their theory and applications in chemistry and molecular and atomic physics. Explicitly correlated wave functions are functions that depend explicitly on interelectronic distance. The book covers a wide range of methods based on explicitly correlated functions written by leaders in the field, including Kutzelnigg, Jeziorski, Szalewicz, Klopper and Noga. The book begins with a chapter on the theory of electron correlation and then the following three chapters describe different types of functions that can be used to solve the electronic Schrödinger equation for atoms and molecules. The book goes on to discuss the effects that go beyond the Born-Oppenheimer approximation, theory of relativistic effects, solution of the Dirac-Colomb equation, and relativistic correction using ECG functions. The last part of the book reviews applications of EC functions to calculate atomic and molecular properties and to study positronic systems, resonance states of atoms and nuclear dynamics of the hydrogen molecular ion.

This second volume of "Progress in Photon Science - Recent Advances" presents the latest achievements made by world-leading researchers in Russia and Japan. Thanks to recent advances in light source technologies; detection techniques for photons, electrons, and charged particles; and imaging technologies, the frontiers of photon science are now being expanding rapidly. Readers will be introduced to the latest research efforts in this rapidly growing research field through topics covering bioimaging and biological photochemistry, atomic and molecular phenomena in laser fields, laser-plasma interaction, advanced spectroscopy, electron scattering in laser fields, photochemistry on novel materials, solid-state spectroscopy, photoexcitation dynamics of nanostructures and clusters, and light propagation.