Nanosecond time-resolved step-scan FT-IR spectroscopy of the photochemical ring-opening of 1,3-cyclohexadiene

Time-resolved step-scan FT-IR spectroscopy with 20 ns resolution has been used to investigate the conformational transformation from cZt-1,3,5-hexatriene to tZt-1,3,5-hexatriene following the photochemical ring opening of 1,3-cyclohexadiene. The step-scan FT-IR spectrometer and an IR flow-cell system for performing UV pump, IR probe experiments with 20 ns time resolution are described. At the earliest measurable time points, only features of the final tZt-hexatriene product were observed in the time resolved spectra. Therefore the time constant for this transformation must be faster than 20 ns.