Presented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978.
Intensities of spin-forbidden transitions in molecular oxygen and selective heavy-atom effects†
Article first published online: 19 OCT 2004
Copyright © 1980 John Wiley & Sons, Inc.
International Journal of Quantum Chemistry
Volume 17, Issue 2, pages 367–374, February 1980
How to Cite
Minaev, B. F. (1980), Intensities of spin-forbidden transitions in molecular oxygen and selective heavy-atom effects. Int. J. Quantum Chem., 17: 367–374. doi: 10.1002/qua.560170219
- Issue published online: 19 OCT 2004
- Article first published online: 19 OCT 2004
- Manuscript Accepted: 25 JAN 1979
- Manuscript Received: 17 SEP 1978
Intensities of a1ΔgX3∑g− and b1∑g+ X3∑g− transitions in molecular oxygen have been calculated on the basis of the INDO method taking into account spin-orbit coupling by perturbation theory. The transitions are magnetic dipole in nature. The first of them (a − X) steals its intensity from 3Πg-3∑g− and 1Πg-1Δg transitions, which are determined by the orbital angular-momentum operator. This source is not the principal one for the intensity of the second (b-X) transition. Its intensity is stolen principally from microwave transitions between spin sublevels of the ground 3∑g− state. The last source explains the large difference in intensities of the a-X and b-X transitions. Calculated oscillator strengths are in a good agreement with experiment. The same integrals that determine the intensity also determine the parameters of the spin Hamiltonian for the ground 3∑g− state. These parameters are in a good agreement with experiment also, showing the validity of the whole calculation. In a condensed phase the investigated transitions are enhanced by intermolecular exchange interaction. It is known that an external heavy atom (EHA) enhances the b-X transition of oxygen in solution, but does not influence the a-X transition. In the collision complex O2-EHA, which has a geometry without inversion symmetry, the microwave transitions between spin sublevels of the “3∑g−” state obtain electric-dipole moments, which are stolen from the charge-transfer transition. This mechanism explains the selective effect of EHA.