Electronic and Vibrational Molecular States

Abstract

This chapter provides the background material for the subsequent development of a microscopic description of charge- and energy-transfer processes in molecular systems. It introduces the molecular Hamiltonian and the respective solutions of the stationary Schrödinger equation. After introducing the molecular Hamilton operator, the chapter discusses the Born–Oppenheimer separation of electronic and nuclear motions as the key to the solution of the molecular Schrödinger equation. It then provides a brief account of electronic structure theory for polyatomic molecules and a short summary of the dielectric continuum model, which allows for incorporation of solvent effects into electronic structure calculations. The chapter also discusses the potential energy surfaces and the related concepts of harmonic vibrations and reaction paths. It focuses on the problem of nonadiabatic couplings, which are neglected in the Born–Oppenheimer adiabatic approximation.