Nuclear Magnetic Resonance Acoustic Absorption in KI and KBr

Abstract

A technique for measuring the coupling between nuclear spins and the crystal lattice is described. The technique is one in which the absorption of energy by the nuclear spins from an acoustic wave is observed as an additional attenuation of the wave in the sample. This attenuation results in a change in the electric impedance of the piezoelectric transducer which drives the sample. The transducer impedance is made to control a Pound-Watkins type of spectrometer through an inverting and matching network.Nuclear Magnetic Resonance acoustic absorption measurements were made on single crystal samples of KI and KBr using compressional waves in the [100] direction. These measurements yield a value of the electric quadrupole coupling ${e}^{2}{q}_{1}Q$, where ${q}_{1}$ is the first derivative with respect to strain of the electric field gradient at the nuclear position. For ${\mathrm{I}}^{127}$ in KI, $\frac{{e}^{2}{q}_{1}Q}{h}=300$ Mc/sec. For ${\mathrm{Br}}^{81}$ in KBr, $\frac{{e}^{2}{q}_{1}Q}{h}=82$ Mc/sec. Interpreting these results on the basis of a point charge model we obtain values of the amplification factor $\ensuremath{\gamma}$. For K${\mathrm{I}}^{127}$, $\ensuremath{\gamma}=38$. For K${\mathrm{Br}}^{81}$, $\ensuremath{\gamma}=26$.