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Lifetime measurements in Si U,

Abstract. We present new laboratory data on the multiplets 2s z IS --2s2p aP, 2s22p 21, _ 2s2p2 4p, and 2s22p 2 zP --2s2p z "5S in nitrogen, oxygen and fluorine, and discuss the Z-dependence of their wave-numbers. These multiplets are very faint in laboratory light sources, but can become prominent in astrophysical sources of low density. Our results confirm the solar identifications of the nitrogen and oxygen multiplets made by Burton et al. Predicted positions of the corresponding multiplets in neon are given.

in an isotope separator to energies between 25 and 85 keV and sent through a carbon foil. The light emitted by the foil-excited particles was analyzed either with a 2 meter Jarrell-Ash monochromator equipped with an EM1 6256 photomultiplier (2 000-Doubly-excited terms in lithium and beryllium.

The contributions of cascades to multi-exponential decay curves are analysed. We define the quantitative cascade contribution to an exponential decay as the replenishment ratio, which is the ratio of the cascade repopulation rate to the decay depopulation rate. We recommend that this ratio be quoted in future papers on beam-foil or other cascade-affected decay measurements. We also present specific relationships between the fitting parameters and the level populations for decay curves which arise from electric dipole transition schemes of up to second order in cascading. Velocity dispersion effects in beam-foil decays are, in general, shown to be negligible, except for decays from ejected foil-particles.