ИСТИНА

The cross sections of the elastic, Stark and Coulomb de-excitation processes in the collisions of muonic hydrogen with hydrogen atom have been calculated in the close-coupling approach taking into account both the closed channels and vacuum polarization shifts of the ns states. In particular, the cross sections of the elastic 2s-2s scattering and Coulomb 2s-1s de-excitation below the 2p threshold, which determine the destiny of a metastable 2s state in muonic hydrogen, were calculated for the first time. The convergence of the cross sections with increasing of the basis states has been investigated. The obtained cross sections were applied as the input data in the detailed studies of the atomic cascade kinetics. The new version of the extended standard cascade model taking into account the initial distributions in the quantum numbers and kinetic energy. In the wide density range a number of characteristics of the atomic cascade have been calculated and compared with the known experimental data: relative yield of the K_alpha-line, arrival population of the 2s-state, population of the 2s metastable fraction (i.e. muonic atom in 2s-states with kinetic energy below 2p threshold), yield of the high-energy (0.9 keV) component of the muonic hydrogen in the ground state , and lifetime of the metastable 2s fraction. The results of the present study prove that the direct Coulomb de-excitation is the dominant mechanism which results in the quenching of the metastable 2s fraction of muonic hydrogen. This mechanism quantitatively explains the formation and the yield of the hot muonic hydrogen in the ground state and leads to the perfect agreement of the calculated and experimental values for lifetime of the metastable 2s fraction.