Transient Field Strength Research Articles

G-Factor of the first 2+ state in theN=82 nucleus138Ba

The 21+ level of138Ba has been Coulomb excited with a 105 MeV32S beam. The precession of the gamma ray angular distribution induced by the transient magnetic field when traversing a 2.14 mg/cm2 iron foil, has been measured to be 15.6(1.7) mr. A value of g(138Ba 21+)=0.72(11) was obtained assuming for the transient field strength the Chalk River calibration. The field parametrization has been checked using the first 2+ state in150Sm as probe. Theg value obtained is sensibly lower than predicted by large scale shell model calculations in a proton subspace. Theg-factor of the first 2+ state in148Sm has been remeasured yieldingg(148Sm 21+)=0.246(22).

Transient fields for W ions traversing Fe hosts and for Os ions traversing Fe and Ni hosts

Transient field strengths were measured for184, 186W ions traversing thin, magnetized Fe foils with velocities in the range 1.8 ≲ υ/υ0 ≲ 5.7 (υ0 = Bohr velocity) and for188, 190, 192Os ions traversing polarized Ni hosts with average velocities 〈υ/υ0〉 ∼ 4. The present measured transient field strengths, together with previously measured results for W, Os ions, are compared with transient field strength parametrizations, and discussed in terms of microscopic models of the transient field.

Transient-field strength measurements for52Cr traversing Fe hosts at high velocity and polarization transfer mechanisms

Transient-field strengths were measured for52Cr ions traversing polarized Fe hosts at velocities up to 12υ0 (12υ0 =c/137 = Bohr velocity). The results are compared with predictions of various transient-field parametrizations and discussed in terms of possible mechanisms by which polarization might be transferred from the Fe host to inner vacancies of the moving Cr ions. Theg-factor of the first 2+ state of52Cr was also measured by the transient-field technique and found to be in accord with shell model calculations.

G-factor measurements in the mercury isotopes

The g-factors of the first 2 + states of 198, 200, 202, 204Hg have been measured using the thin-foil transient field technique. Relative g-factors were obtained and absolute values were deduced by calibrating the field with the known magnetic moment of 198Hg. A pronounced dip was seen for the 200Hg 2 1 + g-factor when compared with the other three isotopes, g-factors of some low-lying states in 199Hg were obtained in the same experiments. The sign of the g-factor of the 3 2 − (208 keV) level appeared to be negative and this was confirmed by an IMPAC measurement in iron. The low transient field strength previously observed for Pt in iron occurs also for Hg in iron.

Transient fields for Ag and Pd ions IN Fe and Co;g-Factor measurements of the lowest 3/2− and 5/2− states in107,109 Ag

Transient field precessions of the 2+1 state of108Pd were measured simultaneously with those of the 3/2−1 and 5/2−1 states of107Ag and109Ag as their ions traversed thin Co and Fe foils. Precessions of the 2+1 states of104,106,108,110Pd were also measured using a natural Pd target evaporated onto 0.9 Μm thick Co. The results of these studies are in accord with prior predictions that the AgFe transient field might be diminished relative to that for PdFe at ion velocities appropriate for molecular orbital vacancy sharing. Transient field strengths for PdCo and PdFe were found to be consistent with scaling according to bulk magnetization of the ferromagnetic host. Gyromagnetic ratios were inferred for the first 3/2− and 5/2− states of107,109Ag relative to theg factor of the 2+1 state of108Pd. Values obtained usingg(2+1;108Pd)=0.36± 0.03 are:g(3/2;107Ag) =0.63±0.09,g(5/2;107Ag)=0.37±0.06,g(3/2;109Ag)=0.77 ±0.10,g(5/2;109Ag)=0.36±0.05.

Scaling of the transient magnetic field with the polarization density of the host

The transient magnetic field strength has been determined accurately for 28Si(2~) at an initial recoil velocity of vi = 1.7 vo (vo = c/137) in magnetized Fe, Co, Ni and Gd. The first-excited state of 28Si was produced with the 28Si(~,~') reaction at E~ = 7.50 MeV. Time-integral rotations of the ~-u angular correlation were measured, which led to transient-field strengths for 2esi in the four ferromagnetic hosts. These strengths were found to scale with the polarization density of the host rather than with the number of polarized electrons per host atom.

Transient fields of linear antenna arrays

An approximate analytical method is presented, which allows calculation of the transient field strength of linear antenna arrays. The detailed investigation of a logarithmicperiodic dipole antenna on the base of different degrees of approximation shows the separate influence of the element radii and the transient mutual coupling between neighbouring elements. For a better physical understanding of its transient radiation process the cylindrical linear antenna when excited by a step-function with finite rise time is discussed in detail presenting an extension of a recently published approximate version of the Singularity Expansion Method to nonzero center-loading.