Postprint version. Published in Physics Letters B, Volume 28, Issue 6, January 6, 1969, pages 406-407.
NOTE: At the time of publication, the author Richard B. Frankel was not yet affiliated with Cal Poly.
The definitive version is available at https://doi.org/10.1016/0370-2693(69)90333-5.
The quadrupole splitting induced by a magnetic field at low temperatures has been measured by Mössbauer spectroscopy for Fe2+ in MgO; a value of +0.21 ± 0.03 barn for the quadrupole moment of 57Fem is obtained.