fluorescence and phosporescence

Greetings:
 	I hope this question is not too far off-topic; it does actually
 relate to my feeble attempts at modeling fluorescent and phosporescent
 materials.
 	I have reviewed a couple of physical chemistry books concerning
 these two topics, and to be quite honest, either they have not explained it
 well, or I am missing the big picture.  If you don't mind, I would like to
 explain to you what I think is going on, and then you could correct me, or
 refer me to some good sources to set me straight.
 Fluorescence:
 A photon comes in and excites a molecule in a ground state (are most ground
 states "singlet states"?) to an excited state (I am assuming that one
 cannot
 excite to a triplet state). There is a percentage or probability that this
 excited state will relax back down to the ground state by emissive means,
 emitting a photon of light that is smaller than the homo-lumo band gap of
 the ground state molecule.  The molecule can also lose its energy through
 non-emissive means such as heat.  The energy cannot move from the excited
 singlet state to a lower energy triplet state due to the need to conserve
 momentum.
 Phosphorescence:  Exitation occurs as above, except energy in this case is
 allowed to move from the excited singlet state to a lower energy triplet
 state through intersystem crossing (which was forbidden in the previous
 scenario).  The triplet state in turn can relax to the (singlet?) ground
 state via emission because of spin orbital coupleing with the heavy
 nucleus).
 Does this sound right?  Have I left something out which is important?
 Thanks.
 Travis Thoms
 Research Associate
 Canon R&D Center Americas. inc.
 Telephone: 1-408-468-2864
 Facsimile:1-408-468-2810
 tthoms;at;cra.canon.com