Spectroscopy of Eu atoms in bulk liquid helium: a novel probe for quantum liquid

The experiment was done in a metal Dewar containing liquid helium. Eu atoms were dispersed into the liquid by photodissociation of Eu particles produced by the laser ablation of Eu sample in the liquid. The second harmonics of a pulsed dye laser beam was used to measure the absorption lines of Eu atom. The laser-induced fluorescence was detected with a photomultiplier through a 25 cm grating monochromator.