High resolution spectral analysis of (CH3OH)-C-13 in the excited torsionalstates

In this work, we have extended our previous analysis of the Hamiltonian of C-13 substituted methanol to include a large number of spectral lines invol ving the second excited torsional state using an improved model. The data s et consisted of 2529 Fourier transform and microwave transitions with the r otational angular momentum J less than or equal to 10, K less than or equal to 6 and n less than or equal to 2 (with 336 MW lines). The data set was f itted with the new Hamiltonian model to derive the molecular parameters. Th e results indicate that the model developed for the other methanol species (CH3OH, (CH3OH)-O-18 and CH3OD) is also valid for the C-13 substituted spec ies. The results will allow the energy levels of the molecule to be calcula ted for higher torsional levels above the internal rotational barrier with improved precision and allow the analysis to be carried out for more excite d torsional states. (C) 2000 Elsevier Science B.V. All rights reserved.