Direct Laser Ionization in Analytically Useful Flames

Direct laser ionization (DLI) proceeds by resonant excitation of analyte followed by photoionization of the excited-state atoms. Photoionization is accomplished with the use of off-resonant radiation, which is usually obtained from the dye laser pumping source. DLI has been shown to enhance ionization yields, relative to laser-enhanced ionization (LEI), in low-temperature atom reservoirs where collisional ionization is inefficient. In the present study, DLI has been demonstrated in high-temperature, analytically useful flames, with similar results. DLI detection limits and spectral interferences, as well as the effects of photoionizing laser power on ionization yield, have been evaluated.