The dipole polarizability and adiabatic correlations of atomic ions are related to the energy levels and oscillator strengths of the levels through bracketing inequalities. For systems with a ground state ns 2 1 S 0 , the total oscillator strength is dominated by the unbranched intrashell ns 2 1 S 0-nsnp 1 P o 1 transition, and the remaining oscillator strength can be narrowly bracketed using the f-sum rule. Thus measurements of the lifetime of the lowest resonance transition can be used to specify the polarizabilities and, alternatively, measurements of the polarizabilities can be used to deduce lifetimes. Moreover, isoelectronic regularities in line strengths can be used to obtain a comprehensive database from a small number of precision lifetime determinations. These methods are applied homologously to produce values for polarizabilities and lifetimes for the Mg, Zn, Cd and Hg isoelectronic sequences. To confirm the reliability of these methods, fast ion beam lifetime measurements in P IV were performed using the arbitrarily normalized decay curve (ANDC) method, and a test of the f-sum was made for Ba II, for which precision measurements of both the polarizability and lifetimes exist.

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Experimental and theoretical values for the lifetimes of the 6s6p 1 P 1 and 3 P 1 levels in the Hg isoelectronic sequence are examined in the context of a data-based isoelectronic systematization. New beam-foil measurements for lifetimes in Pb III and Bi IV are reported and included in a critical evaluation of the available database. These results are combined with ab initio theoretical calculations and linearizing parametrizations to make predictive extrapolations for ions with 84рZр92.

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We report lifetimes, branching fractions, and the resulting oscillator strengths for transitions within the P II multiplet (3s 2 3p 2 3 P − 3s3p 3 3 P o ) at 1308 Å. These comprehensive beam-foil measurements, which are the most precise set currently available experimentally, resolve discrepancies involving earlier experimental and theoretical results. Interstellar phosphorus abundances derived from λ1308 can now be interpreted with greater confidence. In the course of our measurements, we also obtained an experimental lifetime for the 3p4s 3 P o 0 level of P IV. This lifetime agrees well with the available theoretical calculation.