A. R. Kunselman

An experimental study of muonic X-ray transitions in mercury isotopes☆

Abstract Muonic X-ray spectra have been measured for 198–202, 204Hg. These data have been interpreted in terms of a two parameter Fermi distribution for the charge density. We have interred the spectroscopic quadrupole moments (Qs) of some of the 2+ nuclear states. For 199Hg we have determined the spectroscopic quadrupole moments of the first two excited states and the B(E2) connecting these states to the ground state. For 201Hg the ground state quadrupole moment has been obtained as well as several other E2 moments but the interpretation of the data has been hampered by a possible incomplete knowledge of the nuclear scheme of this nucleus. The muonic isotope shifts have been measured and interpreted in terms of σRk and are compared to electronic X-ray and optical isotope shift measurements.

A windowless frozen hydrogen target system

Abstract A cryogenic target system has been constructed in which gaseous mixtures of all three hydrogen isotopes have been frozen onto a thin, 65 mm diameter gold foil. The foil is cooled to 3 K while inside a 70 K radiation shield, all of which is mounted in a vacuum system maintained at 10−9 Torr. Stable multi-layer hydrogen targets of known uniformity and thickness have been maintained for required measurement times of up to several days. To date, hundreds of targets have been successfully used in muon-catalyzed fusion experiments at TRIUMF.

Muonic X-ray study of the charge distribution of 165Ho

Abstract We report the measurement of the energies of 4f → 3d, 3d → 2p, 2p → 1s, 3p → 2s and 2s → 2p muonic atomic transitions in 165 Ho. Using transitions to and from the 1s, 2s, 2p and 3p levels, as well as the hyperfine splittings of the 2p, 3p, and 3d states, we have fitted our data to two distinct deformed Fermi distributions: one with a constant skin thickness; the other with a skin thickness which varies as a function of polar angle. Both yield good fits. The necessity of adding nuclear polarization corrections is demonstrated. The spectroscopic quadrupole moments of the first two nuclear states are determined to be 3.49±0.03 e · b and 3.43±0.04 e · b, respectively. The groundstate intrinsic hexadecapole moment is determined to be 0.50±0.23 e · b 2 .

Experiments with energetic [mu]d and [mu]t emitted from solid hydrogen

A set of experiments is reviewed which makes use of the emission of muonic deuterium from the surface of a layer of solid hydrogen. The behaviour of muons in a solid target system has been studied via detection of muon decay electrons, muonic X-rays, and fusion products (neutrons and charged particles). The emission of muonic deuterium is understood to result from the Ramsauer-Townsend scattering minimum. The energy distribution of the emitted atoms ranges from tenths of eV to about 10 eV, and can be controlled to some extent. A proposal is described to use muonic tritium emission to measure the energy dependence of muonic molecular formation.

Production of slow muonic hydrogen isotopes in vacuum

Muonic hydrogen isotopes (μ− p, μ− d, and μ−t) are simple quantum mechanical systems ideally suited for studies of numerous fundamental phenomena in electroweak and strong interactions as well as in applied areas such as muon chemistry or muon catalyzed fusion.Emission of muonic hydrogen isotopes into vacuum helps to overcome the limitations which are normally imposed on conventional investigations with gaseous and liquid targets. A proof of principle experiment for this new technique was performed at TRIUMF last year. Negative muons with 30 MeV/c momentum were stopped in a thin film of solid hydrogen and produced very low energy μ−d in vacuum. The distribution center of the normal velocity components of emitted μ−d atoms was measured to be ∼1 cm/μs. The yield of μ−d in vacuum is an increasing function of H2 film thickness δ up to a value of δ≥1 mm.

Resonant Formation of d{mu}t Molecules in Deuterium: An Atomic Beam Measurement of Muon Catalyzed dt Fusion

Resonant formation of d&mgr;t molecules in collisions of muonic tritium ( &mgr;t) on D2 was investigated using a beam of &mgr;t atoms, demonstrating a new direct approach in muon catalyzed fusion studies. Strong epithermal resonances in d&mgr;t formation were directly revealed for the first time. From the time-of-flight analysis of 2036+/-116 dt fusion events, a formation rate consistent with 0.73+/-(0.16)(meas)+/-(0.09)(model) times the theoretical prediction was obtained. For the largest peak at a resonance energy of 0.423+/-0.037 eV, this corresponds to a rate of (7.1+/-1.8)x10(9) s(-1), more than an order of magnitude larger than those at low energies.

Muon molecular formation and transfer rate in solid hydrogen-deuterium mixtures

In an experiment at TRIUMF to study muon-catalyzed fusion and associated atomic and molecular effects, negative muons were stopped in a solid protium hydrogen layer containing a small amount of deuterium. Most of the resulting µp atoms disappeared by formation of ppµ molecules or by muon transfer to a deuteron. The µd can drift almost freely through the hydrogen layer due to the Ramsauer-Townsend effect and may even leave the layer. If a thin neon layer is frozen atop the hydrogen, the exiting muonic atoms will very rapidly release their muon to a neon atom. The analysis of the time structure of the neon X-rays is used to determine the rates of the slower processes involved in the evolution of the µp. This analysis has been performed with the help of Monte Carlo calculations, which simulate the kinetics of both µp and µd atoms in the hydrogen mixtures.

A precision determination of the radial charge parameters and the quadrupole moment of 181Ta using muonic X-rays

Abstract We report the measurement of the energies of the 4f → 3d, 3d → 2p and 2p → 1s atomic transitions in muonic 181 Ta. Using transitions to and from the 1s and 2p levels, as well as the hyperfine splittings of the 2p and 3d states, we obtained the radial charge parameters assuming deformed Fermi distributions. We found the intrinsic static quadrupole moment Q 0 = 6.82 ± 0.06 e · b, in excellent agreement with Coulomb excitation results. We verified that the dynamic (corresponding to transitions to the first excited state) and the static (ground state) E2 moments were equal to within 1.1 %. The intrinsic hexadecapole moment was determined to be Π 0 = −0.12 ± 0.40 e · b 2 .

Producing μ−d and μ−t in vacuum

After the feasibility of vacuum isolated μ−d production was demonstrated at TRIUMF in 1989, development was begun on a target system that would take advantage of the process to aid in the understanding of the muon catalyzed fusion cycle. Minimal neutron backgrounds, the ability to use silicon detectors, and compatibility with tritium were considered important for a very versatile target system. The advantages which the target gives in isolating μCF process will be outlined.

Pionic 4f-3d X-rays from 208Pb and 209Bi

Abstract The X-ray energies and widths of the pionic 4f-3d and 5g-4f transitions have been measured in 208 Pb and 209 Bi. The 3d widths obtained are in reasonable agreement with theory, and do not support the anomalously small values previously reported.