Book excerpt: An introduction to one of the fundamental tools in chemical research—spectroscopy and photophysics in condensed-phase and extended systems A great deal of modern research in chemistry and materials science involves the interaction of radiation with condensed-phase systems such as molecules in liquids and solids as well as molecules in more complex media, molecular aggregates, metals, semiconductors, and composites. Condensed-Phase Molecular Spectroscopy and Photophysics was developed to fill the need for a textbook that introduces the basics of traditional molecular spectroscopy with a strong emphasis on condensed-phase systems. It also examines optical processes in extended systems such as metals, semiconductors, and conducting polymers, and addresses the unique optical properties of nanoscale systems. Condensed-Phase Molecular Spectroscopy and Photophysics begins with an introduction to quantum mechanics that sets a solid foundation for understanding the text's subsequent topics, including: Electromagnetic radiation and radiation-matter interactions Molecular vibrations and infrared spectroscopy Electronic spectroscopy Photophysical processes and light scattering Nonlinear and pump-probe spectroscopies Electron transfer processes Each chapter contains problems ranging from simple to complex, enabling readers to gradually build their skills and problem-solving abilities. Written for upper-level undergraduate and graduate courses in physical and materials chemistry, this text is uniquely designed to equip readers to solve a broad array of current problems and challenges in chemistry.