U. Grabowy

Measurements of magnetic moments of 134, 136Xe(2+1) and the mean life of the 136Xe(2+1) state

Abstract The g -factors of the first 2 + states in 134, 136 Xe have been measured relative to the known value of 132 Xe(2 + 1 ) employing the transient-field technique with Fe as ferromagnetic host. Coulomb excitation with sulphur beams was applied to isotopically pure Xe targets. The lifetime of the 136 Xe(2 + 1 ) state has been redetermined using the Doppler-shift attenuation method. The value obtained tends to be shorter than the only published data.

Range and stopping power dependence of heavy ion-induced demagnetizations of ferromagnetic materials

Abstract Heavy ion beams induce by their stopping power severe demagnetizations of ferromagnetic materials of dynamic nature. This perturbation of ferromagnetism causes substantial attenuations of transient magnetic fields on traversing probe ions. A striking stopping power dependence has been found when the probe ions are in the H-like charge state. Due to the uncorrelated behaviour of beam ions and probe ions , moving on different trajectories through the ferromagnetic sample, the demagnetization, initially located at the ionization track of the beam ion, must propagate to the region of the probe ion. The determination of the range of demagnetization from its origin was the subject of the present measurements.

On the ion beam stopping power dependence of transient magnetic fields in Fe- and Gd-hosts

Ion-beam induced attenuations of transient magnetic fields have been further studied in measurements on high-velocity24Mg- and28Si-ions as well as low-velocity48Ti-ions using energetic beams of Ti- and Br-ions. Further evidence for the stopping power dependence of the attenuations is found; more data in the threshold region of Fe-host support earlier observations. In Gd-host the attenuations are again weaker pronounced than in Fe in accordance with previous data.

Preparation and analysis of targets with implanted thick Ar layers for in-beam γ-spectroscopy

Abstract Implantation of 80 keV 40 Ar ions into 0.5 mg/cm 2 thick Fe layers, deposited by vacuum evaporation onto a Gd foil, yielded an Ar target of 35(6) μg/cm 2 thickness which is suitable for in-beam γ-spectroscopy. Thin Fe-layer evaporation and implantation were successively applied in several cycles whereby the Ar implantation always occurred into a newly prepared Fe layer. These procedures can principally be extended for obtaining even larger thicknesses. The Ar content of the target and its layer thickness were accurately determined by the Elastic Recoil Detection Analysis technique using a 58 Ni beam.

Transient magnetic fields and electron polarizations of H-like oxygen ions in crystalline iron and amorphous iron-boron compounds

Abstract Transient magnetic fields (TF) have been measured for oxygen ions with the 16 O(3 − ) state as probe traversing thin layers of crystalline Fe and amorphous Fe 80 B 20 compounds. The TF associated with polarized 1s electrons have strengths of B TF (Fe) = 412 (38) T in Fe and B TF (FeB) = 368 (62) T in FeB implying degrees of polarization of p 1s (Fe) = 0.13 (1) and p 1s (FeB) = 0.14 (3), respectively. The strength parameter a = 12.1 (2.3) T deduced for FeB agrees very well with other data rendering it highly suitable for TF measurements.

AMORPHOUS FE TARGETS FOR TRANSIENT FIELD MEASUREMENTS WITH HEAVY-ION BEAMS

For transient field measurements (TF), ferromagnetic target foils of the amorphous Fe80 B20 compound were prepared with thicknesses between 2 and 8 μm. A minimum thickness of 8 μm was achieved employing a special lapping and polishing technique. For further thickness reduction, the ion-etching technique was used. Very promising results with respect to heavy-ion beam deterioration of TF were obtained in the preliminary measurements with this material.

Spectroscopy of low-lying levels in 81Br and its nuclear-structure interpretation

Abstract Magnetic moments of low-lying levels in 81Br have been measured using Coulomb excitation of 81Br beams and the technique of transient magnetic fields with Gd as ferromagnet. In addition, lifetimes have been redetermined for several states employing the Doppler-shift attenuation method and mixing ratios of γ-transitions were deduced from angular correlations. The data are discussed in the framework of the particle-vibrator and the particle-rotor coupling models.

Large transient magnetic fields of 28Si ions in backscattering through Fe at high velocities

Abstract Transient field (TF) precessions have been measured in Fe for high-velocity 28 Si ions following projectile Coulomb excitation of the first 2 + -state. In contrast to a recent measurement on 24 Mg ions which yielded at comparable velocity with the same geometry for the angular correlation an unexpected small TF, the present observations agree very well with the expectation of large TF: no diminution of the transferred polarization is found.

Magnetic-moment and lifetime measurements of Coulomb-excited levels in 79Br

Abstract The g-factors of the 217, 523 and 761 keV levels in 79 Br have been measured using Coulomb excitation of 79 Br beams and transient field technique with Gd as ferromagnetic host. Lifetimes of several states have been determined using the Doppler-shift attenuation method. Mixing ratios of γ-transitions were deduced from measured angular correlations. The data are discussed in the framework of the weak particle-core coupling and the particle-axial-rotor coupling models.

Quantum beat measurements on spin-polarized electrons in oxygen ions emerging from magnetized Ni- andGd-layers

Employing the time-differential perturbed γ-angular correlation technique it is shown that 1s- and2s-electrons of highly stripped16O(3−)-ions have their spin polarized on emergence from magnetized thin Ni- andGd-layers into vacuum. The mean degree of polarization of 2s-electrons is found to be twice as large as for 1s-electrons.