Rhenium Pure Quadrupole Resonance Spectrum of Potassium Perrhenate

The rhenium pure quadrupole resonance spectrum of polycrystalline potassium perrhenate has been observed. The frequencies of both the $\pm \frac{5}{2}\mathrm{\hspace{0.17em}\leftrightarrow \hspace{0.17em}\pm }\frac{3}{2}$ and $\pm \frac{3}{2}\mathrm{\hspace{0.17em}\leftrightarrow \hspace{0.17em}\pm }\frac{1}{2}$ transitions for ¹⁸⁵Re and ¹⁸⁷Re were found and have the values 56.600, 28.312, 53.626, and 26.825 MHz, respectively, at room temperature. These values are compared with a “theoretical” value of the quadrupole coupling obtained by adding the calculated point‐charge field‐gradient tensor to that arising from the $p$ character of the bonds, both based on an assumed electronic structure for the ReO₄⁻ ion. It is shown that a reasonable value of the polarization factor will provide agreement with experiment.