H. Schneuwly

CHARGE DISTRIBUTION PARAMETERS, ISOTOPE SHIFTS, ISOMER SHIFTS AND MAGNETIC HYPERFINE CONSTANTS FROM MUONIC ATOMS

A compilation of muonic-atom data providing information on the size of nuclei is presented: energies of μ x-ray transitions, theoretical corrections, isotope and isomer shifts, and magnetic hf constants. Besides root-mean-square radii, equivalent radii from a model-independent analysis are given.

Study of X-rays and nuclear γ-rays in muonic thallium

Abstract Energies and intensities of muonic X-rays, nuclear γ-rays and μ-capture γ-rays were measured in natural muonic thallium with Ge(Li) detectors. The absolute intensities of higher μ X-rays were reproduced by a cascade calculation starting with a statistical population at n = 20 including K-, L- and M- conversion. The electron screening effect was deduced from energies of higher μ X-rays. Eight prompt nuclear μ-rays were found, due to an excitation of (4.1 ±1.0) % and (14.6 ± 3.0) % of the first 3 2 + level in μ 203 T1 and μ, 205 T1, respectively, and of (8.8 ± 0.9) % of the 5 2 − level at 2.63 MeV in 205 T1. This excitation explains the anomalous intensity ratios of the 2p-ls and 3d-2p fine structure components. From the nuclear y-rays of the first excited states were deduced: the magnetic h.f. splittings e 203 ( 1 2 ) = 2.57 ± 0.15 keV , e 205 ( 1 2 ) = 2.30 ± 0.02 keV, muonic isomer shifts ΔE is (203) = 0.26 ± 0.15 keV, ΔE is (205) = −(0.31 ± 0.11) keV; E2/M1 mixing ratios δ μ 2 (203) = 0.89 ± 0.27, δ μ 2 (205) = 1.00 ± 0.05, and the half-life in the presence of the muon T μ ( 3 2 ) = 1.4 ± 0.1 nsec in 205 T1. The values of e( 1 2 ) and ΔE ls were compared with shell-model calculations. From δ μ 2 and T gm ( 3 2 ) evidence for a magnetic nuclear polarization was found. From the 2p-ls, 3d-2p, 3p-2s and 2s-2p transitions the size and shape of the nuclear charge distribution and a nuclear polarization due to the 1s 1 2 muon of ΔE np = 8.3 ± 1.2 keV and 9.5 ± 1.2 keV for 203 Tl and 205 T1 respectively were determined in agreement with theoretical estimates. An isotope shift of ΔE = 10.35 ± 0.25 keV was measured for the 1s 1 2 state which is compared with data from optical spectroscopy. From an analysis of the time distribution of delayed γ-rays from μ-capture, an isotopic effect of (5.4 ± 2.5) % was found for the capture rates, in fair agreement with predictions from Primakoffs μ-capture formula.

Nuclear excitation and isomer shifts in muonic atoms: (I). Experiment and evaluation

Abstract Energies and intensities of 53 nuclear γ-lines in muonic atoms of Sm, Gd, Eu, Tm, Yb, Ta, W, Re, Os, Ir, Pt, Hg, Tl, and Bi have been measured with Ge(Li) detectors. By comparison with γ-lines from radioactive sources the isomer shifts for transitions from nuclear rotational levels, quadrupole and octupole vibrational levels, and single-particle levels have been deduced. The effect limiting the accuracy of the extracted isomer shifts is the correction for the magnetic hyperfine splitting of the nuclear levels.

TEST OF QUANTUM-ELECTRODYNAMICAL CORRECTIONS IN MUONIC ATOMS.

Abstract Energies of the 5g-4f muonic X-rays have been measured in nat Hg and 203 Tl with an accuracy of about 25 eV. They are found to be smaller than theoretical energies including recently revised calculations of higher-order vacuum polarization, by about two standard deviations.

Observation of electric quadrupole X-ray transitions in muonic thallium, lead and bismuth

Abstract Electric quadrupole X-ray transitions (5g → 3d, 4f → 2p, and 3d → 1s) have been observed in muonic Tl, Pb and Bi. From the 3 → 1 transitions, energy splittings of the n = 3 levels were deduced. From a comparison of the relative intensities of E1 and E2 transitions, the population ratios 5g 5f , 4f 4d , and 3d 3p were deduced. These ratios are well reproduced by a cascade calculation assuming a statistical initial population at n = 20, including K, L and M shell conversion. In the case of 205 T1 discrepancies between the experimental and the calculated 3d-1s/3p-1s intensity ratio can be explained by nuclear excitation. From the 3 p 3 2 → 1 s 1 2 intensity in 209 Bi we can deduce the ratio of the radiationless to the X-ray transition width and give limits for prompt neutron emission from the 3d level.

Muon capture in 151Eu and 153Eu

Abstract Delayed γ-rays from μ-capture in natural europium were measured with a Ge(Li) detector. From absolute γ-intensities, populations of individual final levels were deduced. In (81±12) % of the μ-capture process, an excited final nucleus was detected. The distribution of excited nuclei is compatible with the neutron multiplicity distribution calculated by Singer; however, the predicted zero neutron emission has not been found. From the analysis of the time distribution of the γ-intensities an isotopic effect for the capture rates was found to be [λ c ( 151 Eu )−λ c ( 153 Eu )]/ λ c = (8.4±2.7) % , which agrees with predictions from Primakoffs μ-capture formula.

Muonic isomer shifts in 153Eu a re-evaluation of Mössbauer isomer shifts in rare earths

Muonic isomer shifts of five γ-ray transitions in 153Eu have been measured and the changes of the mean square radius between the ground and excited states have been derived. With the present data the Mossbauer isomer shifts in rare earths can be re-evaluated.

Magnetic hyperfine splitting of the 2s12 − 2p12 transition in muonic 115In

Abstract In 115In a magnetic hf-splitting of the muonic 2 s 1 2 − 2 p 1 2 transition was observed. From this the hf-constant A 1 (2 s 1 2 ) = 280 ± 60 eV and an improved value A 1 (2 p 1 2 ) = 520 ± 60 eV were deduced. The experimental results are compared to calculations on the basis of the shell model with configuration mixing.

Magnetic hyperfine interaction of the 2+ rotational states in muonic 190,192Os

Abstract In muonic 190,192Os the magnetic hf-spliting of the 2+ → 0+ nuclear transition was measured. The hf-splittings ΔE( 190 Os ) = 665 ± 80 eV and ΔE( 192 Os ) = 800 ± 80 eV of the 2+ state are reduced at 59% compared to a point-like magnetic moment in agreement with the assumption of a magnetization density of a magnetization density distribution proportional to R2 ϱcharge(R) as calculated from a rigid rotator. The influence of these results on the analysis of muonic isomer shifts is pointed out.

Magnetic hyperfine interaction of the 2+ rotational states in muonic os-190,192

Abstract In muonic 190,192Os the magnetic hf-spliting of the 2+ → 0+ nuclear transition was measured. The hf-splittings ΔE( 190 Os ) = 665 ± 80 eV and ΔE( 192 Os ) = 800 ± 80 eV of the 2+ state are reduced at 59% compared to a point-like magnetic moment in agreement with the assumption of a magnetization density of a magnetization density distribution proportional to R2 ϱcharge(R) as calculated from a rigid rotator. The influence of these results on the analysis of muonic isomer shifts is pointed out.