Hyperfine interactions, including Bhf[FrFe], studied in the decay chain of225Ra by alpha and gamma anisotropy measurements

On the absence of appreciable half-life changes in alpha emitters cooled in metals to 1 Kelvin and below

“…The raw data were taken over a period of about 5 days and all decay corrections were made using the simple 3.66 d half-life of 224 Ra. The observed temperature dependence was fitted with the magnetic dipole moment of 212 Bi as the unknown quantity, yielding the value | µ | = 0.41(5) n.m. [3], which is in very reasonable agreement with a subsequent laser-based measurement of 0.32 (4) n.m. [18]. These observations are in complete contradiction to the Full scenario prediction that the the 212 Bi activity would follow a 10.6 h lifetime throughout the low temperature experiment.…”

“…However, 225 Ac has spin 1/2 and for spin 1/2 isotopes no anisotropy is observed in emissions which conserve parity. Thus no orientation detected by alpha or gamma decay should be observed in emissions from either 221 Fr or 217 At in the Full scenario in direct contrast with experiment [3].…”

“…The experiments concern the decay of relatively long lived 224 Rn, 225 Ra and 227 Ac and their daughter decay chains implanted in an iron metal foil and studied at temperatures down to below 20 mK. The original objectives of this work were to study the polarization of the decaying isotopes through measurement of the angular properties of their alpha and gamma emissions -the method of low temperature nuclear orientation (LTNO) -leading to results on the hyperfine interactions of the isotopes involved, their magnetic dipole moments and the magnetic hyperfine fields they experienced as implants in the ferromagnetic iron lattice [2,3,4]. However the results throw direct light upon the suggestions made by Kettner et al in Ref.…”

Hyperfine field of francium in iron

“…9 For 208,211,213 Fr a thoriumdi-phtalo-cyamineϩThC 2 target was used. These isotopes were produced directly and one after the other implanted on line ͑at 60 keV͒ into the same iron foil ͑purity 99.998%, thickness 50 m͒ that was soldered to the cold finger of the NICOLE 3 He- 4 He dilution refrigerator. 10 The 221 Fr source was prepared by implanting 221 Rn (T 1/2 ϭ25 min) produced on a ThC 2 target.…”

“…The hyperfine fields of the alkaline elements are especially important to test different theoretical approaches since the simple electronic structure of alkaline impurities is supposed to facilitate the interpretation of experimental values. For francium two measurements of the hyperfine field in iron have been published up to now, 3,4 with conflicting results. In both cases the method of low-temperature nuclear orientation ͑NO͒ was used.…”