# What exactly happen when 532nm laser cause fluorescence in red objects

I hit the above plastic sliding toys with 532nm Laser in a Raman spectrometer and the following are the spectra of each. This is the blue sliding toy showing the right Raman for the plastic.

But when I hit the red sliding toy, there is no Raman signature detected, instead there is a broad Fluorescence.

What happen exactly at the molecular level when the red object get fluorescence from the 532nm laser but not the blue object?

And if I paint the red object with blue paint, would the fluorescence be suppressed producing the spectrum for the blue object?

• Not exactly. The laser excites both the dye in the blue and in the red material. The blue emission seems to have a max at about $550$ nm (its hard to tell as there are no values on your plot) and the dye in the red material at about $590$ nm. Thus the blue dye has a larger S1-S0 energy gap than the red dye but both are less than the energy of the laser's photon. (i'm guessing that $532$ nm is off the left of either plot.) Aug 27, 2022 at 10:05