This book presents detailed aspects of different fields of molecular spectroscopy. It consists of eleven chapters starting from the Born–Oppenheimer approximation and its relevance to various spectra to some topics on nonlinear spectroscopy through rotational, vibrational, Raman, and electronic spectroscopy, group theoretical application, nuclear magnetic resonance, electron spin resonance, nuclear quadrupole resonance, and Mossbauer spectroscopy. The intention is to present a good background of the theoretical aspects of the concerned fields which will help the readers to understand the...