Excitation fluorescence spectrum:

The excitation spectrum refers to the plot of the emission intensity from the sample at a given wavelength against the wavelength of exciting radiation. This is acquired through observing the fluorescence intensity at a predetermined wavelength and the wavelength of the excitation radiation is varied continuously. Commonly, the excitation spectrum of a molecule is same to its UV-VIS absorption spectrum.

 The following structural characteristics in a molecule might make it fluorescent.

• The presence of benzene ring
• Fused ring system
• Rigidity in the molecule

  The following factors might affect the fluorescence features of a molecule:

• temperature
• pH
• dissolved oxygen
• solvent