  Precise spectroscopic analysis of polyatomic molecules enables many striking
advances in physical chemistry and fundamental physics. We use several new
high-resolution spectroscopic devices to improve our understanding of the
rotational and rovibrational structure of methyltrioxorhenium (MTO), the
achiral parent of a family of large oxorhenium compounds that are ideal
candidate species for a planned measurement of parity violation in chiral
molecules. Using millimetre-wave and infrared spectroscopy in a pulsed
supersonic jet, a cryogenic buffer gas cell, and room temperature absorption
cells, we probe the ground state and the Re=O antisymmetric and symmetric
stretching excited states of both CH3 187 ReO3 and CH3 185 ReO3 isotopologues
in the gas phase with unprecedented precision. By extending the rotational
spectra to the 150-300 GHz range, we characterize the ground state rotational
and hyperfine structure up to J = 43 and K = 41, resulting in refinements to
the rotational, quartic and hyperfine parameters, and the determination of
sextic parameters and a centrifugal distortion correction to the quadrupolar
hyperfine constant. We obtain rovibrational data for temperatures between 6 and
300 K in the 970-1015 cm-1 range, at resolutions down to 8 MHz and accuracies
of 30 MHz. We use these data to determine more precise excited-state
rotational, Coriolis and quartic parameters, as well as the ground-state
centrifugal distortion parameter D K of the 187 Re isotopologue. We also
account for hyperfine structure in the rovibrational transitions and hence
determine the upper state rhenium atom quadrupole coupling constant eQq' .
