Muon transfer from deuterium to helium

Abstract

We report on an experiment at the Paul Scherrer Institute, Villigen, Switzerland measuring x rays from muon transfer from deuterium to helium. Both the ground state transfer via the exotic dmu3,4He* molecules and the excited state transfer from mud* were measured. The use of CCD detectors allowed x rays from 1.5 keV to 11 keV to be detected with sufficient energy resolution to separate the transitions to different final states in both deuterium and helium. The x-ray peaks of the dmu3He* and dmu4He* molecules were measured with good statistics. For the D2+3He mixture, the peak has its maximum at E_dmu3He = 6768 +- 12 eV with FWHM Gamma_dmu3He = 863 +- 10 eV. Furthermore the radiative branching ratio was found to be kappa_dmu3He = 0.301 +- 0.061. For the D_2+4He mixture, the maximum of the peak lies at E_dmu4He = 6831 +- 8 eV and the FWHM is Gamma_dmu4He = 856 +- 10 eV. The radiative branching ratio is kappa_dmu4He = 0.636 +- 0.097. The excited state transfer is limited by the probability to reach the deuterium ground state, q_1s. This coefficient was determined for both mixtures: q^3He_1s = 68.9 +- 2.7% and q^4He_1s = 90.1 +- 1.5.Comment: 9 pages, 11 figure

Experimental study ofμ-atomic andμ-molecular processes in pure helium and deuterium-helium mixtures

“…The prompt intensities are measured within the same time interval as for the pure helium runs, both with and without the delayed electron coincidence condition. The [20] taken at a similar pressure as in run III, are also shown in the table. The differences in relative intensity between pure helium and the deuterium-helium mixtures are essentially due to excited state transfer.…”

“…2. The formation of the dµ 3 He molecule practically coincides with the subsequent γ-ray emission because of the very short average life-time of dµ 3 He molecule (∼ 10 11 s −1 [2,20,22,28,29]).…”

“…-the muon transfer from exited states of (µh) * to helium (occurring in D 2 + 3 He mixtures), t ≤ 10 −10 s [17,19,20,22].…”

“…-initial population of µh and µHe excited states for various deexcitation processes of muonic atoms (e.g., Stark mixing, Auger and Coulomb deexcitation processes [12,13,14,15,16]); -muon transfer between excited states of µh and µHe [16,17,18,19,20];…”

“…-ground state muon transfer from µh to helium via the intermediate 2pσ molecular state, hµHe [24,25,26,27,28], and the subsequent decay to the unbound 1sσ state [2,20,22,29,30].…”