  High-dispersion (channel width 0.015 km s^-1) laboratory spectroscopy of the
torsion-rotation lines J_2 - J_1 (J = 2 - 6) in the ground torsional state (vt
= 0) of the E-type methanol demonstrates multicomponent hyperfine splitting
patterns at 25 GHz. The observed patterns are compared with simulations of
CH3OH emission lines based on ab initio quantum-mechanical models. A
substantial disparity between the laboratory and simulated patterns is
revealed. The observed morphology of the line shapes is not reproduced in the
model profiles. The found inconsistency requires further refinement of the
current quantum-mechanical models to fit the observed hyperfine splitting
patterns at 25 GHz.
