Electric quadrupole interactions of europium in alkali europium tungstates by Moessbauer and laser spectroscopies

151Eu Moessbauer spectroscopy and optical-r.f. double resonance spectroscopy measurements of the quadrupole interaction parameters in KEu(WO4)2 give good agreement and are of comparable accuracy, while laser heterodyne spectroscopy measurements provided improved accuracy by an order of magnitude. However in the crystallographically disordered compound NaEu(WO4)2, Moessbauer spectroscopy was more suited to producing fittable spectra. The difference in the hyperfine field of the two compounds in a 9 T applied field is attributed to a transferred hyperfine interaction. (orig.)