Generation of sub-ps IR pulses via parametric processes and application totransient spectroscopy of molecules

Intense pulses for two-color pump-probe spectroscopy in the mid-infrared sp ectral region are generated by subsequent parametric stages. Frequency down conversion yields pulses from 2.6 to 7 mu m with a duration of 0.5 ps, whi le independent adjustment of the pulse duration is achieved from 0.5 to 2.6 ps. Application of these pulses to transient spectroscopy of a 0.8 M solut ion of HDO in heavy water yields significant vibrational lifetime shortenin g for the OH-mode from 1 ps at 298 K down to 0.5 ps at 268 K for hexagonal ice.