Collisional Quenching of the 2S State of Muonic Hydrogen
  We have calculated differential, total and transport cross sections for muonic hydrogen in the n=2 state scattering from hydrogen. The metastable fraction of the 2S state that slows down below the 2P threshold without undergoing collisional quenching has been calculated as a function of the initial kinetic energy using a Monte Carlo kinetics program. Contrary to earlier estimates, the metastable fraction in the kinetic energy range of 2-5 eV cannot be neglected. 
T. S. Jensen and V. E. Markushin