G.H. Miller

Muonic 197Au: A test of the weak-coupling model☆

Abstract We report the measurement of the energies of various muonic atomic transitions above 500 keV in 197Au. We have used the weak-coupling model in order to analyze the hyperfine structure of 197Au. Using transitions to and from the 1s, 2s 2p and 3p levels as well as the fine structure of the 2p states and hyperfine splittings of the 2p, 3p and 3d states we have fitted our data to two deformed Fermi distributions: one with a constant skin thickness, the other with a skin thickness which varies. Both yield equally good fits. We have determined the quadrupole moment of 197Au to be 0.547±0.016 b. The model dependence of our results is discussed. The weak coupling parameters of de-Shalit Ω p , Ω 22 , Ω 20 and A 2 have been determined and are in fair agreement with Coulomb excitation results. There is also good agreement between our results and those of electron scattering.

Negative muon capture in carbon leading to specific final states

Abstract The yields of γ rays from specific final nuclear states excited following negative muon capture in 12 C have been measured. Using the values for the capture rates to excited states in 12 B and the result of an earlier experiment for the total capture to all bound states in 12 B, we obtain for the durect capture rate to the ground state of 12 B, λ( 12 B gs ) = (6.0 ± 0.4) × 10 3 s −1 . This value is in agreement with theoretical predictions, but the theoretical and experimental uncertainties permit extraction of only a rather imprecise value for the weak-magnetism coupling constant in the muon capture Hamiltonian.

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 .

Determinations of nuclear level halflives in 85Rb and 237Np and their use as timing standards

Abstract The application of nuclear lifetimes in the nonosecond range to the calibration of nuclear timing systems is discussed. More precise measurements of the lifetimes of the 517 keV level in 85 Rb and the 60 keV level in 237 Np are presented.

2s Atomic level in muonic 208Pb

Abstract We report the measurement of the energies and the relative intensities of various muonic atomic transitions above 500 keV in 208 Pb including transitions to and from the 2s level. Besides the usual E1 transitions we have observed 3d → 1s and 4d → 2p E2 transitions. Interpretation of these data in terms of various charge distributions is made. Appreciably better fits are obtained by assuming the presence of nuclear polarization and allowing the nuclear polarization parameters ΔE (1 s ) and ΔE (2 s ) of the 1s and 2s levels to vary. Least-squares fits indicate values of ΔE (1 s ) = −8.9±2.7 keV and ΔE (2 s ) = −0.6±0.7 keV. Comparisons with electron scattering results are made.

Muon capture rates on 16O leading to bound states of 16N

Abstract The partial muon capture rates on 16 O leading to all four particle-stable states in 16 N have been measured. The results obtained are compared to previous measurements and are also used to extract a value for the induced pseudoscalar coupling constant in muon capture.

Strong interaction effects in the 2p-1s transition in pionic neon

Abstract We present experimental results for the 2p-1s transition energy and the natural line-width of the 1s state in pionic neon. The line width ifΓ=14.5 ± 3.0 keV is in substantial agreement with semiphenomenological low-energy pion-nucleus interaction theories in the region A ≈ 20.

The 2s atomic level in muonic 140Ce

Abstract We have observed the 2s → 2p and the 3p → 2s muonic X-ray doublets in 140Ce. Assuming a two-parameter Fermi distribution we find our data are best fit by allowing a 5.4 ± 0.7 keV shift downward in the 1s 1 2 level in reasonably good agreement with the theoretical calculations for nuclear polarization. The sensitivity of our results to a three-parameter Fermi distribution is explored.

Energy and width measurements of the pionic 2p1s transition in 23Na

Abstract New measurements of the energy and natural linewidth of the pionic 2p1s X-ray transition and of the energy of the muonic 2p1s X-ray transition in 23 Na have been performed. A high-resolution Ge(Li) spectrometer was used, resulting in more precise measurements than previously reported. Comparisons are made with the theoretical predictions of the Ericsons.

Nuclear gamma rays in 19F following stopping pions

Abstract The yield per stopped pion of 197 and 109 keV γ-rays in CF 2 has been found to depend on target thickness. The probable excitation mechanism and methods to reduce such yields in studies of muonic and pionic atoms are discussed. More precise determinations of the energies of the first and second excited states of 19 F are listed.