HIGH-RESOLUTION QUANTUM BEAT SPECTROSCOPY IN THE ELECTRONIC GROUND-STATE OF A POLYATOMIC MOLECULE BY IR-UV PUMP-PROBE METHOD

By introducing the IR-UV pump-probe technique to detect molecular quantum beats, this phenomenon is utilized as a Doppler-free time domain spectroscopy for the electronic ground state. The technique is demonstrated with Stark quantum beats of vibrationally excited S0 levels to determine the electric dipole moment, but it can be equally well applied to study structure and dynamics of ground state molecules and radicals. Exciting the aldehydic C-H stretching mode nu2 of propynal, HC-CCHO, a dipole moment was found which is, within experimental error, identical to that previously measured for the vibrational ground state by microwave spectroscopy.