International audienceWe report on time-modulated two-body weak decays observed in the orbital electron capture of hydrogen-like (140)Pr(59+) and (142)Pm(60+) ions coasting in an ion storage ring. Using non-destructive single ion, time-resolved Schottky mass spectrometry we found that the expected exponential decay is modulated in time with a modulation period of about 7 seconds for both systems. Tentatively this observation is attributed to the coherent superposition of finite mass eigenstates of the electron neutrinos from the weak decay into a two-body final state. (c) 2008 Published by Elsevier B.V

We report on the first measurement of the ${\beta }^{+}$ and orbital electron-capture decay rates of ${}^{140}\mathrm{Pr}$ nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike ${}^{140}\mathrm{Pr}^{58+}$ ions is about 50% larger than that of heliumlike ${}^{140}\mathrm{Pr}^{57+}$ ions. Moreover, ${}^{140}\mathrm{Pr}$ ions with one bound electron decay faster than neutral ${}^{140}\mathrm{Pr}^{0+}$ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.

International audienceThe periodic time modulations, found recently in the two-body orbital electron capture (EC) decay of both, hydrogen-like Pr-140(58+) and Pm-142(60+) ions, with periods near to 7 s and amplitudes of about 20%, were re-investigated for the case of Pm-142(60+) by using a 245 MHz resonator cavity with a much improved sensitivity and time resolution. We observed that the exponential EC decay is modulated with a period T = 7.11(11) s, in accordance with a modulation period T = 7.12(11) s as obtained from simultaneous observations with a capacitive pick-up, employed also in the previous experiments. The modulation amplitudes amount to a(R) = 0.107(24) and a(P) = 0.134(27) for the 245 MHz resonator and the capacitive pick-up, respectively. These new results corroborate for both detectors exactly our previous findings of modulation periods near to 7 s, though with distinctly smaller amplitudes. Also the three-body beta(+) decays have been analyzed. For a supposed modulation period near to 7 s we found an amplitude a = 0.027(27), compatible with a = 0 and in agreement with the preliminary result a = 0.030(30) of our previous experiment. These observations could point at weak interaction as origin of the observed 7 s-modulation of the EC decay. Furthermore, the data suggest that interference terms occur in the two-body EC decay, although the neutrinos are not directly observed. (C) 2013 Elsevier B.V. All rights reserved

We have performed a systematic study of the bremsstrahlung emission from the electrons in the plasma of a commercial 14.5 GHz electron-cyclotron resonance ion source. The electronic spectral temperature and the product of ionic and electronic densities of the plasma are measured by analyzing the bremsstrahlung spectra recorded for several rare gases (Ar, Kr, and Xe) as a function of the injected power. Within our uncertainty, we find an average temperature of ≈48 keV above 100 W, with a weak dependency on the injected power and gas composition. Charge state distributions of extracted ion beams have been determined as well, providing a way to disentangle the ionic density from the electronic density. Moreover x-ray emission from highly charged argon ions in the plasma has been observed with a high-resolution mosaic-crystal spectrometer, demonstrating the feasibility for high-precision measurements of transition energies of highly charged ions, in particular, of the magnetic dipole (M1) transition of He-like of argon ions.

The hadronic shift in pionic hydrogen has been redetermined to be ε _1s = 7.086 ± 0.007(stat) ± 0.006(sys) eV by X-ray spectroscopy of ground-state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.