singlet-triplet transitions (spin-flip)

Dear Mihály,
Is it possible to consider singlet-triplet transitions (transition density matrix, not just transition energies) within the non-relativistic (or scalar-relativistic) case (e.g. via CFOUR interface)
within the LR-CC (or MRCI) methods?

According to the manual I guess that the answer is "No" due to impossibility to specify "spin-flip" in the ciguess keyword?


Thank you,
Leonid Skripnikov.

Dear Leonid,
In principle, it is possible between a singlet ground state and a triplet excited state. But these transition moments are zero with non/scalar-relativistic Hamiltonians, or did I misunderstand anything?

>In principle, it is possible between a singlet ground state and a triplet excited state.

OK, but is it possible (in principle) also to consider triplet ground state (i.e. triplet-singlet transitions)?

> But these transition moments are zero with non/scalar-relativistic Hamiltonians, or did I misunderstand anything?

It can be interesting for considering, e.g. M1 (magnetic dipole) transitions with spin-dependent operator.

Best,
Leonid Skripnikov.