Measurements of4s4pP1lifetimes in the ZnI isoelectronic sequence: GaII, GeIII, AsIV

The oscillator strengths for the $4s^2{}_{}{}^1{}_{}{}^{}S-4s4p{}_{}{}^1{}_{}{}^{}P$ resonance line in the ZnI isoelectronic sequence have been obtained for GaII, GeIII, and AsIV by means of lifetime measurements utilizing beam-foil spectroscopy at low initial ion energies. The energy dependence of the emission cross sections for the resonance transition and for the main cascades populating the resonance state in GaII exhibit significantly different energy dependence, which allows an elimination or strong reduction in the influence of the cascades by performing the lifetime measurements at low initial ion energies, for GaII at 100-150 keV. The experimental oscillator strengths are in good agreement with recent calculations by Froese-Fischer and Hansen.