Lifetime and population of muonic hydrogen and deuterium in the metastable 2S state

Recently, the CREMA collaboration succeeded to measure the Lamb shift (2S-2P energy difference) in muonic hydrogen doing laser spectroscopy. In the present study we analyze the data sets taken with muonic hydrogen and muonic deuterium, and investigate the deexcitation of the metastable 2S state of muonic hydrogen and deuterium. We have observed a long-lived and a short-lived component, and determined the populations and lifetimes. Interesting differences between muonic hydrogen and muonic deuterium are revealed. The results serve as an important observable for cascade calculations in exotic atoms. In addition, precise knowledge of populations and lifetimes of the 2S state will enable improvements for the next generation muonic hydrogen 2S-2P spectroscopy experiment.