Determination of the Nuclear Quadrupole Moment of Fe57m from α−Fe2O3 Data

Abstract

A new value for the nuclear quadrupole moment $Q\left({\mathrm{Fe}}^{57m}\right)$ of the 14.4-keV level of ${\mathrm{Fe}}^{57}$ based on $\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$ data has been determined from a detailed series of Mössbauer-effect quadrupole-interaction measurements, x-ray structure-parameter studies, and lattice-sum calculations (including dipole moments). At room temperature, $e^{2}qQ=+0.880\mathrm{}\pm 0.024$ mm/sec. This, when combined with the principal component of the electric field gradient tensor at the iron-ion site (+4.910±${10}^{13}$ esu), yields $Q\left({\mathrm{Fe}}^{57m}\right)=+0.283\mathrm{}\pm 0.035$ b. The calculated field gradient is very sensitive to slight variations in the $\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$ structure parameters, particularly so for the iron special position parameter. A careful analysis has been made of the uncertainty in the quadrupole moment determination, although the effects of covalency and quadrupole (and higher-order) polarizability have not been included. It was also found that the thermal history of the samples can influence significantly the measured quadrupole coupling constant. The present result is compared to other quadrupole moment determinations.