All chemists and many biochemists, materials scientists, engineers, and physicists routinely use spectroscopic measurements and electronic structure computations to assist and guide their work. This book is designed to help the non-specialist user of these tools achieve a basic understanding of the underlying concepts of quantum chemistry. The emphasis is on explaining ideas rather than on enumeration of facts and/or the presentation of procedural details. The book can be used to teach introductory quantum chemistry to second- or third-year undergraduates either as a stand-alone one-semester...