Picosecond infrared double resonance studies on SF6

A classic pump–probe experiment is performed on SF6. Using 30 psec pulses from two independently tunable CO2 lasers, we have studied the intramolecular energy transfer processes occurring in a collisionless environment. Distinct from nanosecond pulse experiments, we find an extremely narrow and deep hole burning feature at the pump wavelength. Experimental results exhibit both discrete state bottlenecking effects and quasicontinuum absorption. New evidence of an extremely rapid collisional relaxation is found, which may be related to rotational hole filling.