Moderation of Negative Mesons in Hydrogen I: Moderation from High Energies to Capture by anH2Molecule

The moderation of negative $\mu$- and $\pi$-mesons, as well as of hypothetical negative particles of mass 1000 m and 1837 m is described for a hydrogen moderator and a meson energy range: 10 Mev→0 ev (capture by an ${\mathrm{H}}_2$ molecule). In this energy range, there are three principal modes of energy loss by the mesons: 1. High energy ionization loss, describable by the ordinary stopping power theory. 2. Energy loss due to nuclear collisions. 3. Low energy ionization loss caused by non-adiabatic processes special to hydrogen. From estimates of the probability of these three processes, the moderation times of a meson in liquid hydrogen from 10 Mev to capture by an ${\mathrm{H}}_2$ molecule are calculated: