R.J. Powers

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 muonic X-ray study of the charge distribution of 144, 148, 150, 152, 154Sm☆

Abstract We report the measurement of the energies of the 4f → 3d, 3d → 2p and 2p → Is muonic atomic transitions in separated isotopes of 144, 148, 150, 152, 154 Sm, and that of the 2s → 2p transitions of 152 Sm as well. Using these transition energies as well as the hyperfine splittings of the 2p levels, we have interpreted our data in terms of a deformed Fermi distribution for the charge density and obtained good fits. A model independent analysis of the isotope shifts in terms of generalized R h moments has been made and is in good agreement with electronic X-ray and optical isotope shifts. The static quadrupole moments and the isomer shifts of the first excited state of 152, 154 Sm have been determined from the 2p hyperfine structure.

Experimental study of pionic Ca and Ti and examination of the pion-nuclear potential for low-Z nuclei

Abstract We report the measurement of the strong interaction shifts and widths of the 3d → 2p transitions in pionic 40,42,43,44,48 Ca and 46,48,50 Ti. Using these new data in combination with earlier low- Z pionic data (6 ≦ Z ≦ 16), we have studied, in a purely phenomenological way, the pion-nuclear optical potential. Employing nuclear-structure information from Hartree-Fock calculations and measured charge densities, we have fitted the pion-nuclear potential parameters to the pionic atom data. The effect of adding an isovector dependence to the s- and p-wave two-nucleon terms has been investigated. We have also explored the sensitivity of these data to the value of the Lorentz-Lorenz parameter ξ. A small but definite sensitivity to the latter parameter has been observed with the best fit value of ξ being significantly greater than 1. We have used the phenomenological potentials to determine the neutron radii of the Ca and Ti isotopes and, in fact, find reasonable agreement with Hartree-Fock predictions and with the results of other hadronic probes.

Pionic 3d → 2p X-ray measurements in 50,52,54Cr, 45Sc, 51V, 55Mn and Fe

Abstract We report the measurement of the strong interaction shifts and widths of the pionic 3d → 2p transitions in separated isotopes of 50,52,54 Cr and natural Sc, V, Mn, and Fe. Using these new data in combination with earlier low- Z pionic data (6 ⩽ Z ⩽ 20) we have studied the phenomenological pion-nuclear potential. Employing nuclear structure information from measured charge densities and Hartree-Fock calculations, we have fitted the pion-nuclear potential parameters to the pionic-atom data. We have explored the sensitivity of these data to the value of the Lorentz-Lorenz parameter ξ. The addition of an isovector dependence to the s- and p-wave two-nucleon terms is shown to be unnecessary at the present level of experimental accuracy. We have used the deduced optical potentials to determine the neutron radii of the nuclei 20 ⩽ Z ⩽ 26 and find reasonable agreement with Hartree-Fock predictions and with the results of other hadronic probes for 20 ⩽ Z ⩽ 23 but poor agreement for 24 ⩽ Z ⩽ 26.

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 .

An experimental study of the EO, E2 and E4 charge moments of 161Dy using muonic atoms

We report the measurement of the energies of 4f → 3d, 3d → 2p and 2p → 1s muonic atomic transitions in 161Dy. The energies have been interpreted in terms of a nuclear charge density which is a five-parameter generalized Fermi distribution. Band mixing effects were taken into account when interpreting the hyperfine structure (h.f.s.). Using the muonic 3d h.f.s. we determined the ground-state spectroscopic quadrupole moment to be 2.468 ± 0.029 e · b. The quadrupole static moments of the first two excited nuclear states of the ground-state band and the transition moments connecting these states to the ground state were determined relative to the ground-state moment by using the muonic 2p h.f.s. The ground-state intrinsic hexadecapole moment was found to be 1.2±0.5 e· b2 using the 3d h.f.s.

Nuclear charge parameters and quadrupole moment in 105Pd from muonic X-rays

Abstract The K and L X-rays of muonic 105 Pd were measured and the radial parameters of the charge distribution in 105 Pd were derived. Based on 2p state hyperfine splitting, the spectroscopic quadrupole moment was determined to be Q s = 0.660(11) e · b.

A muonic X-ray study of the charge distribution of 147Sm AND 149Sm☆

Abstract We report the measurement of the 4f → 3d, 3d → 2p and 2p → 1s muonic atomic transitions in separated isotopes of 147,149 Sm. Using these transition energies as well as the hyperfine splittings of the 2p levels, we have interpreted our data in terms of a deformed Fermi distribution for the nuclear charge density and obtained good fits. A model-independent analysis of the isotope shifts in terms of generalized r k moments has been made and is in good agreement with electronic X-ray and optical isotope shifts. Spectroscopic quadrupole moments and the B( E 2, 7 2 − → 5 2 − ) have been determined from the 2p hyperfine structure.

Electron screening and inner shell refilling in pionic atoms

Abstract Using a bent crystal spectrometer and a Ge detector, we have determined the energies of five pionic transitions possessing sizable electron screening corrections. In three of the cases studied, depletion of the inner-electron shells through Auger processes in preceding cascades is known to occur and these shells may be highly ionized when the pionic X-ray is emitted. In the other two cases studied, no depletion of the 1s electron shell is expected. Our findings for all transitions agree well with the calculated screening correction assuming full electron shells. We conclude that for medium and heavy pionic atoms electronic refilling takes place prior to emission of observable pionic X-rays.

Experimental determination of the relativistic fine structure splitting in a pionic atom

Abstract Using a high-resolution crystal spectrometer, we have measured the energy splitting of the pionic 5g-4f and 5f-4d transitions in Ti. The observed fine structure splitting agrees, within experimental error of 3%, with the splitting arising from the calculated relativistic term and other small corrections for spinless particles.