electronic transitions occur much more quickly than the change in nuclei distances, so only the overlap between initial and final vibrational wavefunctions matters for the probability a transition will occur
non-radiative loss of energy between vibrational energy levels. This excess vibrational energy is lost as kinetic energy to other vibrational modes, either of the same molecule or of a different molecule
type of fluorescence in which an electron relaxes into the ground state via emission of a photon. However, unlike in fluorescence, the electron must change spin states for this to occur. This is a forbidden transition, so happens over a much longer time scale