# 2015 CAP Congress / Congrès de l'ACP 2015

Jun 13 – 19, 2015
University of Alberta
America/Edmonton timezone
Welcome to the 2015 CAP Congress! / Bienvenue au congrès de l'ACP 2015!

## CLS Synchrotron FIR Spectroscopy of High Torsional Levels of CD3OH: The Tau of Methanol

Jun 15, 2015, 4:15 PM
15m
CCIS L2-200 (University of Alberta)

### CCIS L2-200

#### University of Alberta

Oral (Non-Student) / orale (non-étudiant) Division of Atomic, Molecular and Optical Physics, Canada / Division de la physique atomique, moléculaire et photonique, Canada (DAMOPC-DPAMPC)

### Speaker

Dr Ronald Lees (Centre for Laser, Atomic and Molecular Sciences, Department of Physics, University of NB)

### Description

Structure from high torsional levels of the CD$_3$OH isotopologue of methanol has been analyzed in Fourier transform spectra recorded at the Far-Infrared beamline of the Canadian Light Source synchrotron in Saskatoon. Energy term values for $A$ and $E$ torsional species of the third excited torsional state, v$_t$ = 3, are now almost complete up to rotational levels $K$ = 15, and thirteen substates have so far been identified for v$_t$ = 4. The spectra show interesting close groupings of strong high-v$_t$ sub-bands related by Dennison’s torsional symmetry index $/tau$, rather than $A$ and $E$, that can be understood in terms of a simple and universal free-rotor “spectral predictor” chart. The energy curves for the v$_t$ = 3 and 4 ground-state torsional levels pass through several of the excited vibrational states, and a number of anharmonic and Coriolis interactions have been detected through perturbations to the spectra and appearance of forbidden sub-bands due to strong mixing and intensity borrowing.

### Primary author

Dr Ronald Lees (Centre for Laser, Atomic and Molecular Sciences, Department of Physics, University of NB)

### Co-authors

Dr Brant Billinghurst (Canadian Light Source Inc.) Dr Li-Hong Xu (Centre for Laser, Atomic and Molecular Sciences (CLAMS), Department of Physics, University of NB)

 Slides