Mössbauer effect inZn67

Abstract

Nuclear-resonance absorption has been observed with an enriched ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$O absorber, and with sources of ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$ diffused into ZnO, ZnS (both wurtzite and sphalerite), ZnSe, ZnTe, and Cu. Resonance was also observed with a copper host and a natural crystal of sphalerite. The aparatus, capable of handling count rates exceeding 2 × ${10}^5$ counts/sec, could detect resonances of 0.01% depth in the life of a single 10 mCi source. Variations in the integrated areas of peaks in the ZnO-ZnO spectrum are explained by inhomogeneous electric field gradients. Isomer shifts cover a range of 112 μm/sec, and are found (expect for the metallic Cu host) to be linear in lattice spacing. The sign of this relation suggests that the excited-state charge radius exceeds that of the ground state. Calculations show the shifts to be primarily of chemical origin, with only small contributions from the second-order Doppler shift associated with zero-point motion.