Re: [math-fun] laser cool liquids?

If the liquid can be heavily doped with Eu3+ ions, then it's a 'cool trick' : it has two energy levels close to the ground state, and can be pumped into fluorescence by 'depopulating' one of those (7F1 or 7F2) up to a higher level (5D0) from where id drops back emitting red light; each time the equivalent of 200 cm-1 of thermal energy is consumed. Wouter.