Mesonic atoms

Abstract

The properties of mesonic atoms are described. The information which can be deduced about the properties of the π and μ mesons and their interactions with the nucleus is summarized. Experimental results on the nuclear size, meson masses and the π meson-nucleon interaction which have been obtained from a study of the energy levels are discussed. The experimentally determined yields of K and L series x-rays also give information on the processes of de-excitation of mesonic atoms. In particular there is evidence of collision de-excitation which is related to meson transfer in compounds and the formation of mesonic molecules which is observed in liquid hydrogen. Other properties of mesonic atoms at present beyond the reach of experimental investigation are briefly mentioned.