Experimental study of μ-atomic and μ-molecular processes in pure helium and deuterium-helium mixtures

We present experimental results of μ-atomic and μ-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 relative intensities of muonic x-ray K series transitions in (μ^3,4He)^* atoms in pure helium as well as in helium-deuterium mixtures. The dμ³He radiative decay probabilities for two different helium densities in D₂+³He mixture were also determined. Finally, the q_1s^He probability for a dμ atom formed in an excited state to reach the ground state was measured and compared with theoretical calculations using a simple cascade model.