Theoretical electric quadrupole transition probabilities for Ca, Sr and Ba

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Abstract
The 1D-1S quadrupole transition probabilities for Ca, Sr and Ba have been computed using extended GTO and STO valence basis sets and configuration-interaction wavefunctions that include the important core-valence correlation effects. For Ba and Sr, the relativistic contraction of the core orbitals was accounted for in the GTO calculations by a relativistic effective-core potential. The authors' computed Einstein coefficient for Ca of 39.6 s-1 is in excellent agreement with the recent experimental value of 40+or-8 s-1. Their best Einstein coefficients for Sr (44.7 s-1) and Ba (2.98 s-1) imply increasing quadrupole line strengths down the column. Relativistic effects substantially increase the quadrupole Einstein coefficient for Ba.