I am studying fluorescent spectroscopy (laser-induced fluorescence spectroscopy specifically). In a particular atomic spectrum, there are some unexpected lines not associated with any known transitions which are only present in higher density environments and are not associated with any other sample constituents. I am trying to formulate an experiment around this phenomena, but I would appreciate input from the community in regards to potential culprits causing this effect.
My knowledge of fluorescence is a little fresh, but I have tried pinning down some mechanisms, specifically: collisional or resonant energy transfer, intersystem crossing, polarization-induced wavelength shifts*. I am not asking for elaboration on all these terms/concepts, this is just an example of my current train of thought and preliminary research.
If there are other fluorescence-induced actions that alter the spectra, please mention them so that I may look them up. But ultimately my main question boils down to this: Can intramolecular energy transfer and intersystem crossing lead to new transitions?
*As far as I understand this only shifts the spectrum and doesn't lead to new transitions