Theg-factor of the 2+ state of180W and quadrupole moment ratios observed for180W and180Hf by the Mössbauer technique

By Mössbauer absorption experiments the magnetic hyperfine splitting has been observed for the 2+ states of¹⁸⁰W and¹⁸²W in a tungsten iron alloy (3.6 at%W). Since theg-factor of the 2+ state of¹⁸²W is known the measured splitting of the¹⁸²W line could be used for the calibration of the magnetic hyperfine field and the measurement with¹⁸⁰W gave then for the unknowng ₂₊-factor of¹⁸⁰W: $$g_{2 + } (^{180} W) = 0.260 \pm 0.017.$$ By use of a WO₃ absorber the electric quadrupole splittings in the same states were measured. The ratio of the quadrupole moments was derived $$\frac{{Q_{2 + } (^{180} W)}}{{Q_{2 + } (^{182} W)}} = 0.983 \pm 0.022.$$ This ratio is somewhat smaller, but more accurate than the weighted means of previous results and in disagreement with the theoretical prediction. A similar measurement with¹⁷⁸Hf and¹⁸⁰Hf and a HfO₂ absorber gave $$\frac{{Q_{2 + } (^{178} Hf)}}{{Q_{2 + } (^{180} Hf)}} = 1.052 \pm 0.021.$$ This result is larger than the average of previous measurements and agrees with theory. The isomer shifts of the Mössbauer lines of¹⁸⁰W and¹⁸²W were measured for sources in a tantalum metal environment and for absorbers of metallic tungsten. Different signs were observed which indicate that the mean squared charge radius of the 2+ state of¹⁸²W is larger than that of the ground state whereas for¹⁸⁰W the ground state has the larger 〈r ²〉-value.