Nucleargfactors of first2+states in even tungsten nuclei determined by recoil implantation into nickel and cobalt, and the hyperfine field on tungsten nuclei in nickel and cobalt

The ion-implantation-perturbed-angular-correlation technique has been used to measure the Larmor precessions of the first $2^{+}$ excited states of ${}_{}{}^{182,184,186}{}_{}{}^{}\mathrm{W}$ in a ferromagnetic nickel host. The observed angular precessions, corrected for the transient field effect, were $\omega {\tau }_{182}\left(2^{+}\right)=0.159\mathrm{}\pm 0.003$ rad, $\omega {\tau }_{184}\left(2^{+}\right)=0.156\mathrm{}\pm 0.011$ rad, and $\omega {\tau }_{186}\left(2^{+}\right)=0.160\mathrm{}\pm 0.007$ rad. Use is made of the accepted $g$ factor of ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$, $g_{184}\left(2^{+}\right)=0.288\mathrm{}\pm 0.007$, to obtain $H_{\mathrm{hf}}(Ni-\mathrm{W})=(-67\mathrm{}\pm 5)$ kOe at 305 K. The $g$ factors of ${}_{}{}^{182,186}{}_{}{}^{}\mathrm{W}$, determined relative to the known $g$ factor of ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$, are $g_{182}\left(2^{+}\right)=0.271\mathrm{}\pm 0.021$, and $g_{186}\left(2^{+}\right)=0.370\mathrm{}\pm 0.036$. Larmor precessions were also measured for the first $2^{+}$ excited states of ${}_{}{}^{184,186}{}_{}{}^{}\mathrm{W}$ in a ferromagnetic cobalt host. The corrected observed angular precessions were $\omega {\tau }_{184}\left(2^{+}\right)=0.839\mathrm{}\pm 0.019$ and $\omega {\tau }_{186}\left(2^{+}\right)=0.833\mathrm{}\pm 0.015$. The resulting hyperfine field on tungsten in cobalt, assuming $g_{184}\left(2^{+}\right)=0.288\mathrm{}\pm 0.007$, is $H_{\mathrm{hf}}(Co-\mathrm{W})=(-341\mathrm{}\pm 12)$ kOe, and the resulting $g$ factor of the first excited state of ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$, determined relative to $g_{184}\left(2^{+}\right)$ in the cobalt host, is $g_{186}\left(2^{+}\right)=0.358\mathrm{}\pm 0.021$. Agreement between $g_{186}\left(2^{+}\right)$ obtained from using a nickel host and $g_{186}\left(2^{+}\right)$ obtained using a cobalt host was very good, and a weighted average of these two independent measurements gives $g_{186}\left(2^{+}\right)=0.361\mathrm{}\pm 0.018$. Target temperature measurements as a function of beam current were also performed. The observed trend of $g$ with increasing $A$ is not compatible with present theories.