FAR-INFRARED LASER LINES FROM OPTICALLY PUMPED 13CH316OH.

This paper describes far-infrared laser lines, their assignments and spectroscopic molecular parameters for an isotopic modification of methanol **1**3CH//3**1**6OH pumped by an electrically chopped CO//2 laser with a peak power of 25 W and a tuning range of plus or minus 40 MHz. Methanol is a weakly asymmetric top with hindered internal rotation. The permanent dipole moment has components both parallel to and orthogonal to the CH//3 axis, and the typical emission pattern leads to a triad of emission lines which satisfy an approximate combination relation. Five such triads were identified, 3 being associated with the torsional ground state, and 2 with the first torsionally excited state. In the 10R16 case, 5 associated cascade lines were identified, and the data for this pump line was used for deriving molecular constants for the C-O stretch state.