The new technique of modulated adiabatic passage on oriented nuclei (MAPON) is shown to provide self-consistent signs and magnitudes for the principal component of the electric-field-gradient tensor at ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Co}$ nuclei in single-crystal iron. The best result for the mode value is $V_{\mathrm{ZZ}}$=+3.4(5)×${10}^{19}$ V/${\mathrm{m}}^2$. A further test of MAPON using ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ in single-crystal iron yields a quadrupole moment of $Q_{56}$=+25(9) ${\mathrm{fm}}^2$, in excellent agreement with systematics and theory. Experimentally derived distributions in electric field gradients are found to be consistent with sample-preparation procedures. These results firmly establish MAPON as capable of resolving extremely fine features in the electronic charge distribution at nuclear probes and with the wide applicability and sensitivity of nuclear-magnetic-resonance spectroscopy on oriented nuclei.

• Received 28 April 1987

DOI:https://doi.org/10.1103/PhysRevB.37.4911