PULSED-LASER PHOTOLYSIS TIME-RESOLVED FT-IR EMISSION STUDIES OF MOLECULAR-DYNAMICS

Time-resolved Fourier transform infrared (FT-IR) emission experiments are used to study photofragmentation processes, single collision react ions, energy transfer events, and laser-initiated radical-radical reac tions. In the experimental apparatus, a 200-Hz ArF excimer laser is co upled to a commercial 0.01-cm-1 resolution Fourier transform infrared spectrometer. Fringes from the He:Ne reference laser are used for time synchronization of the laser pulses to the FT-IR mirror retardation. Following a short delay after the laser pulse, the analog-to-digital c onverter samples the signal on the infrared detector at several time d elays. A number of fringes are then skipped and the process is repeate d. At the start of the next mirror sweep, data for the first time poin ts are acquired at different mirror positions, and the process is repe ated until multiple interferograms are obtained at all time delays. Th rough the use of improved background-limited detectors and multipass c ollection optics, spectra from a number of small molecules have been o btained in various processes. We report here on the comprehensive deta ils of our experimental apparatus and discuss several of the processes studied with the use of this apparatus.