R.R. Borchers

g-factors for 2+ states of doubly even nuclei (Ge, Se, Mo, Ru, Pd, Cd and Te)

Abstract The gyromagnetic ratio, g, for the first excited 2+ states of 25 even-even isotopes of Ge, Se, Mo, Cd, Pd, Ru and Te were obtained using the ion implantation perturbed angular correlation technique. The g factors were extracted from the measured precession angles using known lifetimes, equilibrium hyperfine magnetic field values and transient hyperfine magnetic field data for fast ions in ferromagnetic lattices. The results indicate that the g factors vary little for the states studied, and are close to the collective value Z/A.

Electromagnetic properties of the first 2+ states of the even Hg isotopes

Abstract The excitation probabilities and the magnetic moments of the first 2 + states of 198 Hg, 200 Hg, 202 Hg and 204 Hg are reported. The energies of the 2 + states and the B (E2) 0→2 values were deduced from the γ-ray spectra observed in a Ge(Li) detector in coincidence with backscattered oxygen ions following Coulomb excitation. The . g -factors of the 2 + states were deduced from integral precession measurements following Coulomb excitation implantation into polarized iron. The results are (relative to 198 Hg: 1.03±0.10, 0.95±0.11, 0.65±0.08, 0.37±0.04 for the B (E2) 0 →2 and 0.55±0.11, 0.43±0.11, 0.59+-0.15, 0.40±0.10 for the g - factors of the 411.8 keV, 368.0 keV, 439.4±0.3 keV and 436.8±0.4 keV 2 + states of 198 Hg , 200 Hg , 202 Hg and 204 Hg respectively. These results do not agree with the predictions of the theory of Kumar and Baranger, but are fairly well reproduced by the calculations of Covello and Sartoris.

Magnetic moment measurements of the first (2+) and second (4+) states of even Nd and Sm nuclei

Abstract The ion-implantation perturbed angular correlation technique was used to measure γ-ray angular distributions from the decay of the first (2 + ) and second (4 + ) states of even Nd and Sm nuclei recoiled into polarized iron. These data and the results of previous measurements give values of H 0 = 2.4±0.3 MOe for H (Nd Fe ), H 0 = 2.3±0.2 MOe for H (Sm Fe ) and H t τ t = 10.8±8.9 MOe · psec for the transient effect for Sm and Nd nuclei recoil implanted into polarized iron (300°K). The g -factor results for the first (2 + ) states of 144,146,148 Nd and 148,150 Sm and for the second (4 + ) states of 150 Nd and 152,154 Sm show a rather strong decreasing trend with decreasing neutron number.

Magnetic moment measurements of the 211.2 keV(32−) and 239.8 keV(52−) states of 195Pt

Abstract The magnetic moments of the 211.2 keV ( 3 2 − , τ = 0.097 nsec) and 239.8 keV ( 5 2 − ,τ = 0.332 nsec) states were measured by recoiling Coulomb excited Pt nuclei into a polarized iron backing foil and observing the precession of the γ-ray angular correlations. The γ-rays were detected in coincidence with backscattered particles with a Ge(Li) detector. The measured precession angles (ωτ) for the 211.2 keV ( 3 2 − ) and 239.8 keV ( 5 2 − ) states are (211.2 keV 3 2 − → 1 2 − ) = 0.080(24), (239.8 keV 5 2 − → 1 2 − )) = 0.135(27), and (140.2 keV 5 2 − → 3 2 − )) = 0.124(48). The g -factors were deduced from these ωτ values after applying corrections for the transient magnetic fields which act on recoiling nuclei. The results are g (211.2 keV) = 0.16(6) and g (239.8 keV) = 0.07 (2) and do not agree with the predictions of the core excitation model.

Revised level scheme of 199Hg following Coulomb excitation

Abstract γ-ray transitions of 199 Hg were investigated following Coulomb excitation with oxygen ions at different bombarding energies. Angular distributions with and without coincidence with backscattered oxygen ions were measured. Ge(Li) γ-ray spectra were measured in triple coincidence with γ-rays and backscattered particles. A new level is reported at 413.5 keV and assigned a spin of 5 2 − . A spin of 3 2 − is assigned to the level at 403.4 keV instead of the 1 2 − spin previously. B (E2)↑ values measured relative to B (E2)↑ (158.37 keV) = 0.375(17) are 0.248(15), 0.170(20) and 0.099(16) for the 208.3, 403.4 and 413.5 keV transitions, respectively. The measured mixing ratios are —0.65(25) and +0.32(2) for the 208.3 ( 3 2 − → 1 2 − ) and 403.4 ( 3 2 − → 1 2 − ) keV transitions, respectively. The revised decay scheme is presented and discussed. The same experimental techniques were used to Coulomb excite 201 Hg. No γ-ray transitions up to an energy of 1000 keV in coincidence with 60 million backscattered particles could be seen when an 85% 201 Hg enriched target was bombarded with 33 MeV 16 O ions.

Gyromagnetic ratios of excited states in 123, 125Te

The results of integral precession measurements are reported for 32+ and 52+ excited states in 123,125Te. The measurements were made using the ion implantation perturbed angular correlation technique by recoiling the excited nuclei into polarized iron. The measured mean lifetimes and g-factors are: 123Te (440 keV, 32+) τ = 39±4 ps, g = 0.34 ± 0.06; (505 keV, 52+) τ = 26±3 ps, g = 0.04±0.025; and 125Te(443 keV, 32+) ρ = 27±3.3 ps, g = 0.39±0.06; (464 keV, 52+) g = 0.12±0.04. The results are compared with theoretical predictions.

Static and transient hyperfine magnetic fields at Ba isotopes recoiled in iron

Abstract The hyperfine magnetic field at Ba nuclei recoiled into Fe is negative and the transient magnetic field acting on the recoiling nuclei is found to be consistent with systematics.

Precession measurements of the 545 keV (6+) rotational state of 154Sm

Abstract The ion implantation perturbed angular correlation technique was used to measure γ-ray angular distributions from the decay of the 545 keV (6+) rotational state of 154Sm recoiled into both copper and polarized iron. The precession angle (ωτ) measured in the polarized iron implantation experiments is consistent with present knowledge of the transient and static magnetic hyperfine fields acting on nuclei recoiled into ferromagnetic hosts. These data and the results of previous measurements give values of Ho = 2.3±0.2 MOe and H1τ1 = 10.7±9.1 MOe · psec for the magnetic hyperfine fields at samarium nuclei recoiled into polarized iron (300°K). The g-factor ratio for the second (4+) and third (6+) excited states of the 154Sm ground state rotational bwand is g 6 + g 4 + = 1.05 ±0.11 .