Energy dependence of the charge exchange reaction from muonic hydrogen to oxygen

Abstract

The charge exchange reaction of negative muons from the $(\mu {\text{p}})_{1{\text{s}}}$ atom to oxygen has been measured in gaseous mixtures of H₂ + O₂. The measurements were performed at three different relative oxygen concentrations ranging from 0.2% to 0.8% and total pressures 3.5–15 bar. A mean transfer rate of $\lambda _{{\text{pO}}}^{\text{t}} = 0.85(2) \times 10^{11} {\text{s}}^{{\text{ - 1}}}$, describing the transfer from the ground state of thermalized $\mu {\text{p}}$ atoms to oxygen, was determined. In order to investigate the energy dependence of the transfer rate, Monte Carlo simulations of the $(\mu {\text{p}})_{1{\text{s}}}$ thermalization and the muon transfer were carried out. The comparison of measured and simulated time spectra yielded an epithermal transfer rate $\lambda _{{\text{pO}}}^{\text{e}}$=3.9 $\times$ 10¹¹ s^-1 in the energy interval 0.12–0.22 eV. The analysis with the model of “Two components” shows that all measured time spectra can be reproduced with the same set of parameters.