Mössbauer Effect withNi61

Abstract

The Mössbauer effect is observed in ${\mathrm{Ni}}^{61}$. The ${\mathrm{Ni}}^{61*}$ was obtained by ${\mathrm{Ni}}^{64}(p, \alpha ){\mathrm{Co}}^{61}\stackrel{{\beta }^{-}\left(99\mathrm{} min\right)}{\to }{\mathrm{Ni}}^{61*}$, giving a nickel Mössbauer nucleus in a ${\mathrm{Ni}}^{64}$ host lattice. The magnitude of the effect at $T=80\mathrm{}°$K is about 4% for a 400 mg/${\mathrm{cm}}^2$ absorber foil (natural nickel). From the thickness dependence we obtain $f_{\mathrm{source}}=f_{\mathrm{abs}}=(9\mathrm{}\pm 1)\%$ for the Debye-Waller factor at $T=80\mathrm{}°$K. The temperature dependence yields a Debye temperature varying between 413° and 437°. The velocity dependence has a half-width of 1.65 mm/sec. The spectrum deviates from the Lorentz shape expected for a single line. A recent electronic determination of the lifetime of this 71-kev state indicates a natural half-width of 0.37 mm/sec. The increased half-width and shape of the spectrum observed in our experiment may be understood in terms of a magnetic hyperfine splitting. The moment of the ground state is known. The internal field $H$ and the magnetic moment ${\mu }_e$ of the first excited state are unknown. An analysis of the data gives a connection between the two quantities, ${\mu }_e\mathrm{}\left(H\right)\mathrm{}$.