triplet excitations with dft and hf

[motago]

 I am trying to calculate the oscillator strength of a singlet ground state to a triplet state excitation.
I've tried that for several molecules, including the simple case of water.
using rpas and rpat, I got oscillator strengths that are of the same order of magnitude of the singlet-singlet excitation.
Selection rules get rid of some of these transitions, but still transitions possible due to spin-orbit coupling get too high oscillator strength. One would expect them to be a few order of magnitude lower than the singlet-singlet ones.
I've used the default basis sets.
I'll be glad to read your comment about that.

[uwe]

Hi,

selection rules for the spin are not included - otherwise all oscillator strengths would be zero for the excitations from singlet to triplet.

Uwe

[motago]

Hi,
I understand the selection rules issue. Still, a singlet-triplet excitation occurs through the spin-orbit operator and it does not make sense to me that the intensity of such transition will be in the same order of magnitude as the singlet-singlet excitations. There should be a few order of magnitude difference.
Can you please respond to that? It is important for me to know if we could use Turbomole for our needs.
Thank you.