Metastable states of the Condo type in exotic helium atoms

We present a precise calculation of the nonrelativistic energies and Auger decay widths for the Condo-type metastable states of exotic helium atoms He⁺X^-, where X^- stands for one of the negatively charged heavy particles μ^-, π^-, or K^-. It has been found that some of the states in muonic and pionic atoms have an anomalously small Auger rate and decay predominantly via slow radiative transitions with the time up to a few hundreds of nanoseconds (muonic atoms) or via a pion decay “at rest” (He⁺π^-).