Sensitive elemental analysis by ArF laser-induced fluorescence of laser ablation plumes: Elucidation of the fluorescence mechanism

Numerous atomic analytes in plumes produced by pulsed-laser ablation fluoresced upon ArF laser irradiation. The likely mechanism was photoexcitation to levels near the ionization limit. These levels were dense and were probably broadened by the extreme plume density to allow efficient absorption of 193 nm photons. The excited atoms relaxed to intermediate states as the plume expanded. Interparticle interaction weakened and transitions from these states produced sharp spectral lines for elemental analysis. This ArF-induced fluorescence technique was orders of magnitude more sensitive than laser-induced plasma spectroscopy.