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 1022 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 1019 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.