Isotopic effect in the decay of antiprotonic helium

An important decay channel of recently discovered metastable antiprotonic helium atoms is the emission of an electron, i.e., the Auger transition. The rate of this process for a number of states of the He-3 (p) over bar e, He-4 (p) over bar e and He-6 (p) over bar e systems is calculated and a substantial isotopic effect is found. While the reduced mass of heavy I,articles increases slightly with increasing nucleus mass, the Auger transition rate decreases by about a factor of three. The explanation of this strong amplification is given and the role of this effect in experiments is discussed.