Gyromagnetic ratio of the 2+ rotational state of184W and observation of a large hyperfine anomaly with respect to183Wg in iron

Theg-factor of the 2⁺ rotational state of¹⁸⁴W was redetermined by an IPAC measurement in an external magnetic field of 9.45 (5)T as: $$g_{2^ + } (^{184} W) = + 0.289(7).$$ In the evaluation the remeasured half-life of the 2⁺ state: $$T_{{1 mathord{left/ {vphantom {1 2}} right. kern-nulldelimiterspace} 2}} (2^ + ) = 1.251(12)ns$$ was used. TDPAC-measurements with a sample of carrierfree¹⁸⁴Re in high purity iron gave the hyperfine fields: $$B_{300 K}^{hf} (^{184} W_2 + underline {Fe} ) = 70.1(21)T$$ and $$B_{40 K}^{hf} (^{184} W_{2^ + } underline {Fe} ) = 71.8(22)T.$$ A comparison with the hyperfine field known from a spin echo experiment with¹⁸³W _g Fe leads to the hyperfine anomaly: $$^{184} W_{2^ + } Delta ^{183} W_g = + 0.145(36).$$ The hyperfine splitting observed in a Mössbauer source experiment with another sample of carrierfree^184m Re in high purity iron indicates that the smaller splitting, measured previously by a Mössbauer absorber experiment is due to the high tungsten concentration in the absorber. The new value for theg-factor of the 2⁺ state together with the result of the Mössbauer experiment allow an improved calibration for our recent investigation of theg _R -factors of the 4⁺ and 6⁺ rotational states. The recalculated values are: $$g_{4^ + } (^{184} W) = + 0.293(23)$$ and $$g_{6^ + } (^{184} W) = + 0.299(43).$$ The remeasured 792-111 keVγ-γ angular correlation $$W(Theta ) = 1 - 0.034(4) cdot P_2 + 0.325(6) cdot P_4 $$ gives for the mixing ratio of theK-forbidden 792keV transition: $$delta ({{E2} mathord{left/ {vphantom {{E2} {M1}}} right. kern-nulldelimiterspace} {M1}}) = - left( {17.6begin{array}{*{20}c} { + 1.8} { - 1.5} end{array} } right).$$ A detailed investigation of the attenuation ofγ-γ angular correlations in liquid sources of¹⁸⁴Re and^184m Re revealed the reason for erroneous results of early measurements of the 2⁺ g _R -factor: The time dependence of the perturbation is not of a simple exponential type. It contains an unresolved strong fast component.