Fourier transform spectroscopy of the CO-stretching band of O-18 methanol

The high-resolution Fourier transform spectrum of the ν8 CO-stretching band of CH318OH between 900 and 1100 cm−1 has been recorded at the Canadian Light Source (CLS) synchrotron facility in Saskatoon, and the majority of the torsion-rotation structure has been analyzed. For the νt = 0 torsional ground state, subbands have been identified for K values from 0 to 11 for A and E torsional symmetries up to J values typically well over 30. For νt = 1, A and E subbands have been assigned up to K = 7, and several νt = 2 subbands have also been identified. Upper-state term values determined from the assigned transitions using the Ritz program have been fitted to J(J + 1) power-series expansions to obtain substate origins and sets of state-specific parameters giving a compact representation of the substate J-dependence. The νt = 0 subband origins have been fitted to effective molecular constants for the excited CO-stretching state and a torsional barrier of 377.49(32) cm−1 is found, representing a 0.89% increase over the ground-state value. The vibrational energy for the CO-stretch state was found to be 1007.49(7) cm−1. A number of subband-wide and J-localized perturbations have been seen in the spectrum, arising both from anharmonic and Coriolis interactions, and several of the interacting states have been identified.