Ground-state muon transfer from deuterium to [Formula Presented] and [Formula Presented]

We have observed the deexcitation x-ray spectra of the exotic molecules [Formula Presented] and [Formula Presented] with good statistics and low background. From the time distributions of these x rays, we have directly determined the muon transfer rates from ground-state muonic deuterium atoms to helium nuclei. The obtained transfer rates in gaseous mixtures at [Formula Presented] K are [Formula Presented] to [Formula Presented] and [Formula Presented] to [Formula Presented] In liquid mixtures, we measured the muon transfer rates [Formula Presented] and [Formula Presented] These transfer rates have to be multiplied with the target density and the atomic helium concentration to obtain the “effective transfer rates” for a specific target composition. The expected isotopic effect between mixtures containing [Formula Presented] and mixtures containing [Formula Presented] as well as with respect to the hydrogen-helium case, is clearly confirmed. A density effect was observed for both isotopic compositions. We investigated the widths and the energies of the intensity maxima of the observed energy spectra of the molecular x rays. From the comparison of the measured energy spectra with calculated ones, we conclude that decay from the rotational state [Formula Presented] of the muonic molecule dominates over decay from [Formula Presented] at the investigated experimental conditions.