Detection of KCl and KOH using collinear photofragmentation and atomic absorption spectroscopy

Summary form only given. Detection of KCl and KOH molecules using direct absorption measurement is a difficult task as the molecular spectra at UV wavelengths is broad and interfering absorption caused by other molecules is evident. In addition, measurement of small concentrations requires a large interaction length due to small absorption coefficient. It was shown that much more selective and sensitive measurement will be achieved using the UV pulse to dissociate K atom from KCl molecule and using atomic absorption spectroscopy to detect the temporally increased atomic concentration. [1] Atomic spectroscopy yields to increased sensitivity and selectivity due to narrow line width of atomic spectrum.In this work, we combine KOH measurement together with KCl measurement using the same continuouswave IR laser to probe the atomic K absorption. Fig. 1 shows the principle of collinear photofragmentation and atomic absorption spectroscopy. Separate UV-pulses are used to dissociate KCl and KOH molecules at different time, separated by few microseconds. The wavelengths of UV-pulses are selected to maximize the selectivity in detection between the molecules. Experiments are carried out in single particle combustion reactor measuring KCl and KOH molecules from the flame area of the burning solid fuel during the complete combustion reaction.The new measurement concept allows laboratory scale measurements directly from the hot flue ga s´ which i s not possible or extremealy difficult by other means. The technique can be extended to all kind of molecules and environments´ where it i s possible to dissociate single atoms from molecules using optical pumping and further detect the increaced atomic concentration with sensitive and selective atomic absorption spectroscopy in collinear arrangement with the pump light source.