Formation and collisional quenching of the long-lived2sstate of muonic hydrogen

Abstract

Ab initio study of the density-dependent population and lifetime of the long-lived ({mu}p){sub 2s} and the yield of ({mu}p){sub 1s} atoms with kinetic energy 0.9 keV have been performed. The direct Coulomb 2s{yields}1s de-excitation is proved to be the dominant quenching mechanism of the 2s state at kinetic energy below 2p threshold and explain the lifetime of the metastable 2s state and high-energy 0.9 keV component of ({mu}p){sub 1S} observed at low densities. The cross sections of the elastic, Stark, and Coulomb de-excitation processes have been calculated in the close-coupling approach taking into account both the closed channels and vacuum polarization shifts of the ns states. The cross sections are used as the input data in the detailed study of the atomic cascade kinetics. The theoretical predictions are compared with the known experimental data at low densities. The 47% yield of the 0.9 keV ({mu}p){sub 1s} atoms is predicted for liquid-hydrogen density.