F. Hagelberg

Transient field precessions and electron polarizations for sulphur ions at high velocity

Effective transient magnetic fields have been measured for S ions traversing thin ferromagnetic foils of Fe, Ni and Gd at mean velocities of 8.0v0 (v0 =c/137). The deduced polarizations attached to 1s electrons are discussed together with all data available for light ions considering spin exchange scattering as polarization mechanism.

Strong enhancement of transient magnetic fields in Gd over Fe for oxygen ions at high velocities

Precision data on transient magnetic fields (TF) in ferromagnetic Gd and Fe were obtained for oxygen ions at velocities between 2 and 8v0 (v0=c/137) using the16O(3−) state as probe. At the high velocities the TF in Gd were found to be twice as large as in Fe which is in contrast to the generally observed scaling with the polarization density of the hosts.Degrees of polarization could be deduced from TF strengths using measured ion fractions of singly occupiedK-shell. The values derived were compared with theoretical estimates based on spin exchange scattering as a possible polarization mechanism.

New aspect in transient magnetic fields using heavy ion beams

Transient field precessions have been measured with the first excited 21+-state as probe for ions of28Si traversing Fe at vion−1v0 and 13v0(v0=c/137) and62Ni being stopped in Fe. The degree of polarization deduced for the Si ions, p1s=0.19(6), is consistent with low-velocity data. There is clear evidence that the field strength is attenuated by heavy ion beams. For the62Ni(21+) state at 1.173 MeV a g-factor value of g=0.34(7) was obtained in good agreement with a previous result.

TransientK-shell hyperfine fields and deduced polarizations for single-electron C and O ions in different ferromagnets

Effective transient magnetic fields have been measured for single-electron carbon and oxygen ions traversing ferromagnetic Ni and Gd hosts, respectively. The deduced values ofK-shell polarization are well explained considering spin exchange scattering as a dominant mode of polarization.

Spin exchange scattering as the most likely polarization mechanism in transient magnetic fields

Salient features of transient magnetic fields, like the degree of polarization, host dependence etc. emerging from studies of high velocity single-electron light ions,Z ≦ 16, are well described by spin exchange scattering as the polarization transfer mechanism. Inclusion of density enhancement effects of the electrons of the solid in the Coulomb field of the moving ion are necessary for a quantitative understanding of the observed large degrees of polarization of the ions.

Large transient magnetic fields for single electron O ions on a 10 fs time scale

Abstract Large transient magnetic fields have been observed for single-electron O ions for short interaction times of 10 fs and 100 fs passing through thin magnetized Gd layers. The derived value for the degree of polarization, p ¯ 1 s = 0.26 ( 1 ) , demonstrates that the polarization transfer cross sections are large enough to generate in very short times substantial polarization of 1s electrons in these ions.

Large dynamic perturbations of transient magnetic fields induced by heavy ion beams

Measurements of transient magnetic fields in Fe for Coulomb-excited24Mg(2↓)-ions at high velocity confirm strong attenuations as observed earller for single-electron28Si ions. In a measurement in which the beam was stopped in a non-magnetic buffer layer sandwiched between the target and the Fe layer the perturbation was shown to result from the interaction of the heavy Ni beam with the ferromagnet. The attenuations seem to be correlated with the dE/dx of the beam-ions in the ferromagnet.

The effect of helium layers implanted into thin iron foils on transient magnetic fields

Abstract Spin precessions in transient magnetic fields (TF) have been measured with the 16 O(3 − ) state as probe for oxygen ions recoiling through localized helium layers implanted into thin iron foils. Precession angles are determined to high precision for different foil thicknesses. The data can be understood only if one assumes that the TF is not operative over the helium implanted region of the ferromagnetic foil. This behaviour indicates that the iron lattice is severely damaged and loses magnetic properties by the implantation process.

Transient magnetic fields for highly stripped ions traversing ferromagnetic solids

Transient magnetic fields experienced by nuclei of single-electron ions in ferromagnetic solids have been analyzed in terms of the polarization of 1s electrons. Values obtained are well explained with spin-exchange scattering.In measurements for Si and Ni ions in Fe and Gd host at high and low velocity, respectively, it is demonstrated that the field strength also depends on the ion beam used for excitation of the nucleus. This new feature has direct relevance in the understanding of previous data.

Measurements of lifetime andg-factor of the 32S(4 1 + ) state at 4.459 MeV

Precessions of the very short-lived 21+ - and 41+-states in32S have been measured using the transient field technique. The deducedg-factor of the 41+-state g=+0.40(15) agrees with the known value of the 21+-state and with theoretical predictions. In addition, the lifetimes of both states were redetermined and are consistent with previous results.