hi i have still some troubles to understand phosphorescence: http://en.wikipedia.org/wiki/Phosphorescence" [Broken] wikipedia has a diagram, where an electron in an exicted state that is a singulet state falls on a second level that is a triplet state. my problem is, that this first transition is explained by spin-orbit coupling. but is it no so, that the ground state and this triplet state should have spin-orbit coupling either?- but in this case, the transition from the triplet state to the ground state should also be possible. so it is possible to have this coupling just between some states? sorry about my english.