Abstract

Methanol is one of the simplest molecule capable of large amplitude torsional motion. This couples with the vibrational motions and has significant effects on the infrared spectrum, illustrated at low resolution in Fig. 1 for the ¹³CD₃OH isotopomer in the 950-1450 cm^-1 region. The complex torsion-vibration energy structure of ¹³CD₃OH is shown in Fig. 2. Level crossings occur among a variety of states giving numerous Fermi and Coriolis interactions. Thus, methanol offers a good test platform for the study of intramolecular vibrational relaxation (IVR) with torsional effects. Furthermore, the ready availability of different isotopomers allows us to seek insight into individual torsion-vibration interaction mechanisms through the substantial changes in symmetry coordinate mixing and vibrational interaction which occur upon isotopic substitution. So far, different bands of ¹³CH₃OH, CH₃¹⁸OH, CD₃OH and ¹³CD₃OH as well as the normal ¹²CH₃¹⁶OH species have all been studied by several groups around the world.^1-7

© 1993 Optical Society of America