This book is dedicated to the description and application of various different theoretical models to identify the near and mid-infrared spectra of symmetric and spherical top molecules in their gaseous form. Theoretical models based on the use of group theory are applied to rigid and non-rigid molecules, characterized by the phenomenon of tunneling and large amplitude motions. The calculation of vibration-rotation energy levels and the analysis of infrared transitions are applied to molecules of ammonia (NH3) and methane (CH4). The applications show how interactions at the molecular scale modify the near and mid-infrared spectra of isolated molecules, under the influence of the pressure of a nano-cage (the substitution site of a rare gas matrix, clathrate, fullerene or zeolite) or a surface, and allow us to identify the characteristics of the perturbing environment. This book provides valuable support for teachers and researchers but is also intended for engineering students, working research engineers and Master's and doctorate students.

This book is dedicated to the description and application of variousdifferent theoretical models to identify the near and mid-infrared spectraof symmetric and spherical top molecules in their gaseous form.Theoretical models based on the use of group theory are applied to rigidand non-rigid molecules, characterized by the phenomenon of tunnelingand large amplitude motions. The calculation of vibration-rotationenergy levels and the analysis of infrared transitions are applied tomolecules of ammonia (NH3) and methane (CH4).The applications show how interactions at the molecular scale modifythe near and mid-infrared spectra of isolated molecules, under theinfluence of the pressure of a nano-cage (the substitution site of a raregas matrix, clathrate, fullerene or zeolite) or a surface, and allow us toidentify the characteristics of the perturbing environment.This book provides valuable support for teachers and researchers but isalso intended for engineering students, working research engineers andMaster s and doctorate students.