Radical theory of hydride atomization confirmed after four decades – determination of H radicals in a quartz hydride atomizer by two-photon absorption laser-induced fluorescence

In an externally heated quartz atomizer, the most often used hydride atomizer for atomic absorption spectrometry, two-photon absorption laser-induced fluorescence (TALIF) was employed (i) to bring after four decades for the first time conclusive proof of the existence of H radical population sufficient to atomize hydrides thus confirming unambiguously the radical theory of hydride atomization and (ii) to determine the distribution of H radicals in the atomizer. Under typical operating conditions, H radicals are concentrated in an approximately 3 mm long cloud in the center of the optical arm and their peak concentration exceeds 10(22) m(–3), i.e. four orders of magnitude above the typical analytical concentration of hydride. The lowest detectable H radical concentration is in the order of 10(19) m(–3). The superb power of TALIF to determine the spatial distribution of H radicals in hydride atomizers for atomic absorption/fluorescence provides a route for elegant optimization of hydride atomization – just by establishing how the atomizer design and parameters influence the distribution of H radicals.