Knowledge Bank

Step-scan FTIR spectroscopy is a new technique whereby the moving mirror in the spectrometer is moved in discrete steps rather than in a continuous fashion. It can be used for time-resolved spectroscopy of infinitely repeatable phenomena by moving the mirror to a fixed position (HeNe fringe), triggering the phenomenon and recording the temporal evolution of the light signal. The mirror is stepped to the next position, and the procedure repeated. At the end of the experiment, the data are transposed into interferograms corresponding to different times after trigger, and subsequently Fouriertransformed to yield time-resolved spectra [1,3]. The time resolution that can be achieved is limited only by the response speed of the detector and acquisition electronics, as well as the detector sensitivity. Until recently most step-scan TRS studies have been limited to emission experiments [4], or experiments in the visible and near-visible regions where the detectors have greater sensitivity [5]. We report new YLiF laser emission data that demonstrate temporal resolutions into the 10s of nanoseconds domain. We also report time-resolved spectra in the mid-infrared in absorption mode of the photochemical reaction $Cl\cdot +C2H6⟶HCl+C2H5\ast$ with microsecond temporal resolution. Further possibilities of the technique for time-resolved spectroscopy are considered.