LASER SPECTROSCOPY OF ANTIPROTONIC HELIUM-ATOMS

The PS205 experiment at LEAR was initiated after we discovered at KEK that about 3% of p's stopped in liquid helium show anomalously long li fetime of about 3 mu s. Our success in 1993 to observe laser-induced r esonant IS annihilation firmly established that the anomaly is due to the formation of an exotic 3-body ''atomcule'', consisting of an elect ron, an antiproton and an alpha particle. Subsequent. progress in expe rimental and theoretical studies of this interesting system is discuss ed.