February 16, 2009 at 1:45 pm | sam | nerd, science@home

I was watching bad TV the other day, and I got bored and started playing with a cool LED pen Thorlabs gave me. I was also drinking some VS (the cheap stuff) Courvoisier cognac. I was surprised to see fluorescence coming from the cognac when illuminated with the blue LED (the fluorescence is the greenish glow):

I suppose that it shouldn’t be surprising, given that cognac is so aromatic! But a visible absorption and green fluorescence isn’t from benzene or something—it’s from a real fluorophore. Cool.

So I wonder what fluorophore is in cognac. I know that coumarin (general structure above) is found in some plants, such as cinnamon, and some coumarins absorb in the blue. And there are a lot of tannins in wooden barrels.

I found these fluorescence spectra of brandy (B), whisky (W), slivovice (S), and juniper spirit (J). Note that the brandy—cognac is a brandy—does fluoresce in the blue/green.