This book combines in one concise volume diverse work on molecular physics. It is designed to serve the needs of graduates and undergraduates in physics, biochemistry and chemistry. Each chapter is self-contained, illustrations accompany the material and some sample problems are worked out. Mathematics that obscures the essence of physics is avoided. The book aims at teaching, and not simply pursuing scientific knowledge. The material is kept as diverse as possible. It is mainly theoretical, but important experimental aspects are also discussed. The book can be used both as a textbook and a reference. The main features covered include - quantum-mechanic 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).