[Paolo M]

The difference is basically clear. Not in the specific.

Light quanta hits the sample, part of the energy is absorbed for an electrons promotion on higher energy levels.

According to Plank law E=hv, lower energy means lower wave numer or higher wavelength (if the light is absorbed, "Stockes-Raman scattering")

So now.. If I position the detector at 90° to the light source I will see a light peak with higher wavelength (flourescence).
Directly in front of the light source I just see a lower light intency but at the same wavelength (absorption).

Why?  

Maybe, i can see both effects in both positions, but looking from 180° position the peak of the light source is simply hidding the fluorescence effect?

Thanks

PS I'm sorry if there are some mistakes, english is not my motherlanguage