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 reactions, energy transfer events, and laser-initiated radical-radical reactions. In the experimental apparatus, a 200-Hz ArF excimer laser is coupled 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 converter samples the signal on the infrared detector at several time delays. A number of fringes are then skipped and the process is repeated. At the start of the next mirror sweep, data for the first time points are acquired at different mirror positions, and the process is repeated until multiple interferograms are obtained at all time delays. Through the use of improved background-limited detectors and multipass collection optics, spectra from a number of small molecules have been obtained in various processes. We report here on the comprehensive details of our experimental apparatus and discuss several of the processes studied with the use of this apparatus.