ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ab initio spin-orbit matrix elements 〈3P2|Hso|3P2〉 and 〈3P1|Hso|1P1〉 have been computed for Mg, Ca, and Sr by using large Slater basis sets and the microscopic spin-orbit Hamiltonian. Results obtained at the valence, core-valence, and singles-plus-doubles configuration interaction level demonstrate the importance of including core-valence correlation. Oscillator strengths for the dipoleallowed 1P1-1S0 transition computed at the core-valence level are also in excellent agreement with experiment. Combining these results leads to radiative lifetimes for the 3P1 metastable states of 4.16 ms for Mg, 0.34 ms for Ca, and 21.2 μs for Sr. These are in good accord with experiment if the class of longer lifetimes is selected for Mg and the class of shorter lifetimes is selected for Ca. The present theoretical study establishes the following two points. First, that deviations from the Landé interval rule are an accurate reflection of the 〈3P1|Hso|1P1〉 matrix element for the heavier alkaline earths (Sr and Ba), but not for Mg, where spin-spin effects are comparable. Second, that the inclusion of direct relativistic effects is not necessary for quantitative agreement with the observed 3P1 lifetimes. Thus it appears that one is justified in using the Breit interaction as a first-order perturbation to describe radiative transitions occurring through off-diagonal mixing with intermediate states.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560260842
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