Proceedings PaperFemtosecond infrared spectroscopy and molecular dynamics
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We recently developed a very sensitive infrared detector having a time response of Ca. 200 fs. The principle involves gating the JR by means of upconversion in a nonlinear crystal. The gating pulse is obtained from a fs dye laser operating at ca. 1 kllz. By means of this device it was possible to determine intensity changes of ca. i:iO in a CW diode or CO laser beam. As a result transient JR studies of moderate vibrational transitions such as found for the carbon monoxide, has been possible at Ca. 200 fs time resolution. The transient JR spectra of samples perturbed by both visible (or UV) and JR pulses has now been accomplished. The 1 kllz source ofshort JR pulses originates from a parametric amplifier pumped by halfthe output ofa regenerative amplifier system that is freguency doubled in KTP. The idler consists of a synchronously pumped dye laser amplified by the other half of the regen output. Experiments using either optical or JR pumping along with JR probing will be reported for a variety of systems including metal carbonyls and hemoproteins. The photofragments, free CO, vibrational energy relaxation and excited states of the organometallics are simultaneously studied. Recent work on molecular reorientation dynamics and determination of transition moment directions using JR/JR probing will be presented.