Knowledge Bank

The spectrum of the first overtone OH stretch band $(2\nu 1)$ in jet-cooled methanol has been measured using Infrared Laser Assisted Photofragment Spectroscopy (IRLAPS) and detailed assignments have been made. In addition to the torsional fundamental band $(\delta vt=0)$ it was possible to observe and assign the torsional combination band with ($\delta vt=1$ and 2). These transitions are very week but can be clearly resolved in the spectra. In total, 131 transitions reaching 19 different K levels in the $2\nu 1$ state have been fit to a global torsion-rotation Hamiltonian and the leading torsion-rotation parameters have been determined. Assignments for the much weaker and irregular torsional band structure for $3\nu 1+\nu 12$ and $3\nu 1+2\nu 12$ are in progress.