FTIR Spectra and Torsion-Vibration Coupling in 13CD3OH

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