This book combines in one concise volume the diverse work of several similar books in the market. Each chapter is self-contained and designed to serve the needs of graduates and undergraduates in physics, biochemistry and chemistry. Numerous illustrations accompany the material and more than 60 problems in molecular physics are worked out. Tedious mathematics that obscures the essence of physics is avoided. Though mainly theoretical, many important experimental aspects are included and discussed. It aims at teaching, and not commenting on scientific knowledge. An essential compendium, it can be used both as a textbook and a reference.The main features covered include: Quantum-mechanical treatment of molecular physics; theoretical treatment of molecular spectra and experimental techniques in spectroscopy; interatomic interactions, potentials, molecular stability, energy levels, bonds, rotational and vibrational states, anharmonicity, polarization; theoretical consideration of real molecules. Resonance methods (NMR, NQR, EPR and ENDOR. Theory, experimental apparatus, techniques, numerical results, applications and utility thereof).