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We report the first experimental determination of the collision-energy dependence of the muon transfer rate from the ground state of muonic hydrogen to oxygen at near-thermal energies. A sharp increase by nearly an order of magnitude in the energy range 0 - 70 meV was found that is not observed in other gases. The results set a reliable reference for quantum-mechanical calculations of low-energy processes with exotic atoms, and provide firm ground for the measurement of the hyperfine splitting in muonic hydrogen and the determination of the Zemach radius of the proton by the FAMU collaboration., 30 pages, 10 figures

The FAMU experiment aims to measure for the first time the hyperfine splitting of the muonic hydrogen ground state. From this measurement the proton Zemach radius can be derived and this will shed light on the determination of the proton charge radius. In this paper, we describe the scientific goal, the method and the detailed preparatory work. This includes the outcome of preliminary measurements, subsequent refined simulations and the evaluation of the expected results. The experimental setup being built for the measurement of the hyperfine splitting to be performed at the RAL laboratory muon facility is also described.

From magnetic, specific heat, (170)Yb Mössbauer effect, neutron diffraction, and muon spin relaxation measurements on polycrystalline Yb(2)Sn(2)O(7), we show that below the first order transition at 0.15 K all of the Yb(3+) ions are long-range magnetically ordered and each has a moment of 1.1 μ(B) which lies at ≃ 10° to a common fourfold cubic axis. The four sublattice moments have four different directions away from this axis and are therefore noncoplanar. We term this arrangement splayed ferromagnetism. This ground state has a dynamical component with a fluctuation rate in the megahertz range. The net ferromagnetic exchange interaction has an anisotropy that favors the local threefold axis. We discuss our results in terms of the phase diagram proposed by Savary and Balents [Phys. Rev. Lett. 108, 037202 (2012)] for a pyrochlore lattice of Kramers 1/2 effective spins.

Interface dislocations present in a Si0.85Ge0.15/Si sample have been imaged using the channeling scanning transmission ion microscopy (CSTIM) method with a 2 MeV proton beam 200 nm across. Groups of parallel dislocations gave dark bands of contrast down to ∼1.5 μm across, the contrast arising from dechanneling of the beam by the bent lattice planes. Tilting of the sample caused the band contrast to change and gave quantitative data concerning the local bending of the lattice planes. A low‐angle boundary model was developed to describe the effect of the groups of dislocations on the channeling contrast. Channeling and topography contrast were obtained from mesa structures present on the sample. Improvements in the sensitivity of the CSTIM method are discussed. The dislocations in the sample were initially characterized by transmission electron microscopy.

Ionizing radiation such as photons, keV electrons, or MeV ions can generate electron‐hole pairs in semiconducting material. The high penetrating power of MeV light ions allows them to generate electron‐hole pairs from deep within intact microelectronic devices, so images can be formed of the device active areas with very little degradation of the spatial resolution of the focused MeV ion beam. Furthermore, the ion‐beam‐induced charge (IBIC) image contrast is not strongly affected by the energy loss through the overlying device layers. This article is the first to demonstrate the capability of a nuclear microprobe to generate IBIC images of the active regions of devices through the passivation and metallization layers. The effect of the carrier generation volume on IBIC resolution is assessed. The ability of IBIC to align the major crystal axes of semiconductor samples is shown, and the effect of ion‐induced damage on IBIC image contrast is considered.

We report a study of the geometrically frustrated magnetic material Tb2Sn2O7 by the positive muon-spin relaxation technique. No signature of a static magnetically ordered state is detected while neutron magnetic reflections are observed in agreement with a published report. This is explained by the dynamical nature of the ground state of Tb2Sn2O7: the Tb3+ magnetic moment characteristic fluctuation time is approximately 10(-10) s. The strong effect of the magnetic field on the muon-spin-lattice relaxation rate at low fields indicates a large field-induced increase of the magnetic density of states of the collective excitations at low energy.

This letter demonstrates that ion channeling patterns, produced by the passage of 3 MeV protons through a 0.5 μm thick [001] silicon crystal, can be transported and manipulated to produce enlarged or reduced area patterns using magnetic quadrupole lenses. The different effects on the ion channeling patterns obtained by using single quadrupole lenses and quadrupole multiplets are shown. The maximum attainable magnification under present conditions is investigated and a fundamental limitation to this process is identified as being the energy spread gained by the proton beam as it passes through the crystal.

The recently developed ion beam induced charge technique has been used to image bands of misfit dislocations in a 4 μm thick epitaxial layer of Si 0.875Ge0.125 grown on a Si substrate. The smallest resolvable bandwidth is 0.8 μm under present conditions. The factors which presently limit this value, and methods for improving it are discussed.

By combining the results of muon spin relaxation and inelastic neutron scattering in the heavy fermion compounds Ce1-xLaxAl3 (0.0or=xor=0.2), we show that static magnetic correlations are suppressed above a characteristic temperature, T*, by electronic dissipation rather than by thermal disorder. Below T*, an energy gap opens in the single-ion magnetic response in agreement with the predictions of the anisotropic Kondo model. Scaling arguments suggest that similar behavior may underlie the "hidden order" in URu2Si2.

Using neutron diffraction, 170Yb Mössbauer and muon spin relaxation spectroscopies, we have examined the pyrochlore Yb2Ti2O7, where the Yb3+S' = 1/2 ground state has planar anisotropy. Below approximately 0.24 K, the temperature of the known specific-heat lambda transition, there is no long range magnetic order. We show that the transition corresponds to a first-order change in the fluctuation rate of the Yb3+ spins. Above the transition temperature, the rate, in the GHz range, follows a thermal excitation law, whereas below, the rate, in the MHz range, is temperature independent, indicative of a quantum fluctuation regime.

This paper shows ion channeling images of the strain field produced by precipitate particles in a crystal matrix. Images have been produced by mapping the energy of 3 MeV protons transmitted through a thinned silicon crystal containing colonies of copper silicide particles, with the incident beam at or close to planar channeling directions of the lattice. Features of the precipitate contrast observed as a function of beam tilt angle away from channeling alignment are qualitatively explained using a model based on symmetrical plane rotation of the crystal lattice around the colonies. © 1996 American Institute of Physics.