Experimental study of $\mu$--atomic and $\mu$--molecular processes in pure helium and deuterium--helium mixtures

Abstract

We present experimental results of $\mu$--atomic and $\mu$--molecular processes induced by negative muons in pure helium and helium--deuterium mixtures. The experiment was performed at the Paul Scherrer Institute (Switzerland). We measured muonic x--ray $K$ series transitions relative intensities in $({\mu }^{3,4}\mathrm{He}{)}^{\ast }$ atoms in pure helium as well as in helium--deuterium mixture. The muon stopping powers ratio between helium and deuterium atoms and the $d{\mu }^3\mathrm{He}$ radiative decay probability of for two different helium densities in ${\mathrm{D}}_2+{}^3\mathrm{He}$ mixture were also determined. Finally, the ${\mathrm{q}}_{1s}^{\mathrm{He}}$ probability for a $d\mu$ atom formed in an excited state to reach the ground state was measured and compared with theoretical calculations using a simple cascade model.

15pages, 10 figures