This book provides a straightforward introduction to the spectroscopy of diatomic molecules and is written at the level of intermediate undergraduate courses in physical chemistry and chemical physics. Following a general introduction to the subject, the second chapter lays out the essential quantum mechanical tools required to understand spectroscopy. Very little previous knowledge is assumed; mathematics is kept to a minimum, the treatment being only semi-quantitative. The following chapter uses this quantum mechanical framework to establish the selection rules which govern spectroscopic...