A hybrid Fourier transform infrared (FTIR) / quantum cascade laser (QCL) spectrometer is introduced for the analysis of gas-phase chemical kinetics, including the study of alkyl halide photolysis reactions. The FTIR provides broadband spectral survey information and the QCL laser system provides improved detection limits and acquisition speeds, albeit over limited wavelength domains. A kinetic model for the photolysis of methyl iodide is introduced which suggests that both the steady state products, such as methanol, and transient intermediates may be monitored using the hybrid setup. Preliminary results use an external cavity QCL to rapidly measure the spectrum of methanol from 2200-1960 cm-1 in ~2 seconds, which is sufficiently fast to capture the chemical dynamics predicted by the model to occur during the first several seconds of photolysis.
|