The concept of adiabatic electronic potential-energy surfaces, defined by the Born?Oppenheimer approximation, is fundamental to our thinking about chemical processes. Recent computational as well as experimental studies have produced ample evidence that the so-called conical intersections of electronic energy surfaces, predicted by von Neumann and Wigner in 1929, are the rule rather than the exception in polyatomic molecules. It is nowadays increasingly recognized that conical intersections play a key mechanistic role in chemical reaction dynamics. This volume provides an up-to-date overview of the multi-faceted research on the role of conical intersections in photochemistry and photobiology, including basic theoretical concepts, novel computational strategies as well as innovative experiments. The contents and discussions will be of value to advanced students and researchers in photochemistry, molecular spectroscopy and related areas.

This invaluable book presents a systematic exposition of the current state of knowledge about conical intersections, which has been elaborated in research papers scattered throughout the chemical physics literature.

It is widely recognized nowadays that conical intersections ofmolecular potential-energy surfaces play a key mechanistic role in thespectroscopy of polyatomic molecules, photochemistry and chemicalkinetics. This invaluable book presents a systematic exposition of thecurrent state of knowledge about conical intersections, which has beenelaborated in research papers scattered throughout the chemicalphysics literature.

The concept of adiabatic electronic potential-energy surfaces, defined by the Born-Oppenheimer approximation, is fundamental to our thinking about chemical processes. Recent computational as well as experimental studies have produced ample evidence that the so-called conical intersections of electronic energy surfaces, predicted by von Neumann and Wigner in 1929, are the rule rather than the exception in polyatomic molecules. It is nowadays increasingly recognized that conical intersections play a key mechanistic role in chemical reaction dynamics. This volume provides an up-to-date overview of the multi-faceted research on the role of conical intersections in photochemistry and photobiology, including basic theoretical concepts, novel computational strategies as well as innovative experiments. The contents and discussions will be of value to advanced students and researchers in photochemistry, molecular spectroscopy and related areas.

Pt. I. Fundamental aspects and electronic structure. 1. Conical intersections in organic photochemistry / M.A. Robb. 2. Efficient excited-state deactivation in organic chromophores and biologically relevant molecules: role of electron and proton transfer processes / A.L. Sobolewski and W. Domcke. 3. Three-state conical intersections / S. Matsika. 4. Spin-orbit vibronic coupling in Jahn-Teller systems / L.V. Poluyanov and W. Domcke. 5. Symmetry analysis of geometric-phase effects in quantum dynamics / S.C. Althorpe -- pt. II. Dynamics at conical intersections. 6. Conical intersections in electron photodetachment spectroscopy: theory and applications / M.S. Schuurman and D.R. Yarkony. 7. Multistate vibronic dynamics and multiple conical intersections / S. Faraji, S. Gomez-Carrasco and H. Koppel. 8. Conical intersections coupled to an environment / I. Burghardt [und weitere]. 9. Ab initio multiple spawning: first principles dynamics around conical intersections / S. Yang and T.J. Martinez. 10. Non-Born-Oppenheimer molecular dynamics for conical intersections, avoided crossings, and weak interactions / A.W. Jasper and D.G. Truhlar. 11. Computational and methodological elements for nonadiabatic trajectory dynamics simulations of molecules / M. Barbatti, R. Shepard and H. Lischka. 12. Nonadiabatic trajectory calculations with ab initio and semiempirical methods / E. Fabiano [und weitere]. 13. Multistate nonadiabatic dynamics "on the fly" in complex systems and its control by laser fields / R. Mitric, J. Petersen and V. Bonacic-Koutecky. 14. Laser control of ultrafast dynamics at conical intersections / Y. Ohtsuki and W. Domcke -- pt. III. Experimental detection of dynamics at conical intersections. 15. Exploring nuclear motion through conical intersections in the UV photodissociation of azoles, phenols and related systems / T.A.A. Oliver [und weitere]. 16. Interrogation of nonadiabatic molecular dynamics via time-resolved photoelectron spectroscopy / M.S. Schuurman and A. Stolow. 17. Pump-probe spectroscopy of ultrafast vibronic dynamics in organic chromophores / N.K. Schwalb [und weitere]. 18. Femtosecond pump-probe polarization spectroscopy of vibronic dynamics at conical intersections and funnels / W.K. Peters, E.R. Smith and D.M. Jonas

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 concise book introduces and discusses the basic theory of conical intersections with applications in atomic, molecular and condensed matter physics. Conical intersections are linked to the energy of quantum systems. They can occur in any physical system characterized by both slow and fast degrees of freedom - such as e.g. the fast electrons and slow nuclei of a vibrating and rotating molecule - and are important when studying the evolution of quantum systems controlled by classical parameters. Furthermore, they play a relevant role for understanding the topological properties of condensed matter systems. Conical intersections are associated with many interesting features, such as a breakdown of the Born-Oppenheimer approximation and the appearance of nontrivial artificial gauge structures, similar to the Aharonov-Bohm effect. Some applications presented in this book include - Molecular Systems: some molecules in nonlinear nuclear configurations undergo Jahn-Teller distortions under which the molecule lower their symmetry if the electronic states belong to a degenerate irreducible representation of the molecular point group. - Solid State Physics: different types of Berry phases associated with conical intersections can be used to detect topologically nontrivial states of matter, such as topological insulators, Weyl semi-metals, as well as Majorana fermions in superconductors. - Cold Atoms: the motion of cold atoms in slowly varying inhomogeneous laser fields is governed by artificial gauge fields that arise when averaging over the fast internal degrees of freedom of the atoms. These gauge fields can be Abelian or non-Abelian, which opens up the possibility to create analogs to various relativistic effects at low speed.