Precision spectroscopy of antiprotonic atoms

Precision spectroscopy of antiprotonic atoms will be an important subject to be pursued at the new antiprotonic decelerator (AD) facility being completed at CERN. In particular, the study of antiprotonic helium atoms, pe/sup -/He/sup 2+/ identical to pHe/sup + /, first discovered at KEK and studied in detail at low-energy antiproton ring (LEAR), will continue to be one of the most important subjects at AD. Our recent high-resolution laser spectroscopy of pHe /sup +/ has reached a precision of 0.5 ppm, and the agreement between our experimental values of transition energies and the calculations has become better than 1 ppm. This agreement in turn sets a severe constraint on the antiproton charge and mass. Future possibilities at AD will be discussed. (18 refs).