$^{17}$O NMR Study of Under-doped Single Crystals of the High Temperature Superconducting Compound Hg1201

We present measurements of $^{17}$O high field NMR on oxygen isotope exchanged under-doped single crystals of the single layer superconductor,$^1$ HgBa$_{2}$CuO$_{4+\delta}$, a compound having a known tetragonal lattice. Our $^{17}$O data for two under-doped samples (T${_c}$ of 87\,K and 79\,K) indicates that there are two inequivalent oxygen planar sites based on measurements of upper and lower quadrupolar satellites. Spectra were taken with 4 K $< T <$ 400 K and 6 T $< H <$ 30 T with a goniometer to precisely orient crystals relative to the magnetic field. We found an asymmetry in the line shape between the upper and lower satellites that cannot be accounted for by a model with a single planar oxygen site. Comparison will be made to earlier work$^2$ on under-doped YBa${_2}$Cu${_3}$O$_{7-y}$. \noindent [1] A.M. Mounce, {\it et al.}, Phys. Rev. Lett. {\bf 111}, 187003 (2013).\\ \noindent [2] T. Wu {\it et al.} Nature Comm. {\bf 4}, 2113 (2013).