RELATIVISTIC Z-DEPENDENCE OF THE OSCILLATOR-STRENGTHS FOR BE-LIKE IONS

The Z-dependence of the oscillator strengths for the intercombination transition (2s2)S-1(0) --> (2s2p)P-3(1) and the resonance transition ( 2s2)S-1(0) --> (2s2p)P-1(1) along the Be-isoelectronic sequence is stu died by analyzing the excitation energies and line strengths from the configuration interaction calculations with a relativistic hydrogenic basis. Eigen equations for the two-configuration final states and thre e-configuration initial state are solved both numerically and analytic ally, and the analytic expressions are further expanded in power serie s of the relativistic parameter (Zalpha)2. While approximating the exa ct numerical results well, these analytic formulas provide the Z-depen dence description of the oscillator strengths along the Be-isoelectron ic sequence. To provide an overall agreement with experiment and with other theories, however, a screened relativistic hydrogenic basis must be used.