Quadrupole Interaction inSb121by Mössbauer Techniques

Mössbauer techniques have been used to study the quadrupole resonance of ${\mathrm{Sb}}^{121}$ in cubic ${\mathrm{Sb}}_2$ ${\mathrm{O}}_3$ (senarmontite). The interaction constant was measured to be $e^{2}qQ=+557\mathrm{}\pm 20$ MHz; except for the sign, this had earlier been determined more accurately by electric-quadrupole-resonance measurements. The sign, which implies a negative electric field gradient, is consistent with a partially covalent bonding of the $5p$ electrons to the three nearly coplanar oxygen atoms surrounding each antimony atom. The previously unknown quadrupole moment of the first excited ${\frac{7}{2}}^{+}$ state is found by measuring $R=\frac{Q\left({\frac{7}{2}}^{+}\right)}{Q\left({\frac{5}{2}}^{+}\right)}$; its value is found to be 1.38±0.02. Then, using $Q\left({\frac{5}{2}}^{+}\right)=-(0.54\mathrm{}\pm 0.07)$ b from optical spectroscopy, $Q\left({\frac{7}{2}}^{+}\right)=-(0.75\mathrm{}\pm 0.09)$ b.