Knowledge Bank

Microwave spectra of $Ar-CH3OH,Ar-CD3OH$, and $Kr-CH3OH$ have been obtained using a pulsed nozzle Fourier transform microwave spectrometer. For each of these complexes two torsional states are observed at the $\sim 1K$ rotational temperature of the expansion. These are the ground state and a metastable excited internal rotor state which correlates to the E internal rotor state of methanol. The a-type ground state spectra are well characterized by the usual asymmetrical top formalism while the excited internal rotor states are complicated by the internal angular momentum. Attempts are presently underway to analyze the excited state spectra. Some preliminary spectroscopic constants for the ground internal rotor state of $Ar-CH3OH$ complex are (in MHz): [FIGURE] The rare gas atom is located approximately perpendicular to the C-O axis. For $Ar-CH3OH$ the distance between the centers of mass of the two subunits is 3.68 A and the weak bond stretching force constant is 0.017 mdyn/A.