Spinforbidden radiative decay involving quasidegenerate states. Application to the B ^{1}Sigma ^{ + } > a ^{3}Π transition in MgO
Abstract
The spinorbit induced interactions among the lowlying X, B ^{1}Σ^{+}, a ^{3}Π, A ^{1}Π, and c ^{3}Σ^{} states of MgO are studied with emphasis on the experimentally observed B ^{1}Σ^{+}→a ^{3}Π spinforbidden dipoleallowed radiative transition. A dressed diabatic states approach is used in which the spinorbit induced perturbation of the (zeroth order) a ^{3}Π_{0}_{+} and a ^{3}Π_{1} fine structure states is partitioned into a contribution from the zeroth order X ^{1}Σ^{+}_{0+} and A ^{1}Π_{1} states and contributions from all other remaining states of ^{1}Σ^{+}_{0+} and ^{1}Π_{1} symmetry. This perturbationpartitioning approach extends a recently developed technique for determining spinorbit perturbed wave functions directly in the CSF basis based on first order perturbation theory [J. Chem. Phys. 83, 1168 (1985)] to situations involving quasidegenerate electronic states. The wave functions in question are expanded in second order configuration state function spaces of between 60 000100 000 terms. The parallel [ μ_{∥}(B ^{1}Σ^{+}_{0+}, v=0; a ^{3}Π_{0}_{+} v=n)] and perpendicular [ μ_{⊥}(B ^{1}Σ^{+}_{0+}, v=0; a ^{3}Π_{1}, v=n)] components of the spinforbidden dipoleallowed transition moment for the B ^{1}Σ^{+}, v=0→a ^{3}Π, v=n transition were obtained. It was found that μ_{⊥}(B ^{1}Σ^{+}_{0+}, v=0; a ^{3}Π_{1}, v=n) peaks at n=1 and that for 0≤n≤3 we have μ_{⊥}(B ^{1}Σ^{+}_{0+},v=0; a ^{3}Π_{1}, v=n) >μ_{∥} (B ^{1}Σ^{+}_{0+},v=0; a ^{3}Π_{0+},v=n)]. The spinorbit induced mixings of the zeroth order X ^{1}Σ^{+}_{0+} and A ^{1}Π_{1} states with the a ^{3}Π_{0+} and a ^{3}Π_{1} states are responsible for the preponderance of the observed B→a (0,0) and (0,1) transition moments.
 Publication:

Journal of Chemical Physics
 Pub Date:
 December 1988
 DOI:
 10.1063/1.455263
 Bibcode:
 1988JChPh..89.7324Y
 Keywords:

 Electron States;
 Forbidden Transitions;
 Magnesium Oxides;
 Radiative Lifetime;
 SpinOrbit Interactions;
 Configuration Interaction;
 Electron Transitions;
 Magnetic Dipoles;
 Radiative Transfer;
 Vibrational Spectra;
 Atomic and Molecular Physics