Infrared–microwave double resonance in methanol: coherent effects and molecular parameters

Infrared–microwave double resonance is studied on five sets of coupled transitions involving torsionally excited states of the vibrational ground state and of the CO-stretch state, and A-state asymmetry splitting parameters are determined. The line shapes show dynamic Stark splitting at low pressure and are dominated by stimulated Raman scattering at high pressure. By analyzing the line shapes in the density-matrix formalism for arbitrary field strength and broadening, we determine the CO-stretch transition dipole moment and extract collision rates for both the CO-stretch state and the vibrational ground state.