microwave influence on Manganese(II) intra-shell transition (advanced question inside)

hboy007, Sun Nov 25 2012, 11:57AM

I can't come up with an explanation as to why the luminescence of Mn(II) 4T1 -> 6A1 transitions is enhanced through microwave influence on the 6A1 ground state. This is claimed by Godlewski et al.

It is stated that the spin-flip and parity forbidden transition (only enabled by weak spin-orbit coupling or mixing with 4p states) is enhanced by "a spin flip in the 6A1 groud state". So nearby Manganese ions couple slightly, enabling some sort of cross-relaxation process which depends on the exact spin orientation of the ground state ion.

Either I am lacking some basic understanding or the explanation is incomplete. How can electron spin resonance account for the relaxation of selection rules? As far as I understand, ESR magnetic dipole transitions should only alter the projection quantum number m_S. Of course, one might also "flip a spin in the ground state", but then the total spin momentum is 3/2, not 5/2. The occupation of orbitals would remain unchanged (this leaves pairing energies and ligand field split terms unchanged) but I can't find a hint anywhere what energy a S=3/2 t_2g^3, e_g^2 (tetrahedral symmetry) state should have.

The only thing I have is the Tanabe-Sugano crystal field splitting diagram

with the 6A1 ground state, neglecting zeeman terms.


Another description of the intra-shell transition is given here:



Please help me!