Determination of the magnitude and sign of the 185,187Re nuclear electric quadrupole coupling constants using nuclear acoustic resonance.

Abstract

Acoustic nuclear electric quadrupole resonance spectra and the magnitude and sign of the coupling constants for {sup 185}Re and {sup 187}Re in rhenium-metal single crystals have been measured using nuclear acoustic resonance (NAR) in a small magnetic field. These measurements were carried out using a NAR reflection bridge spectrometer in the 37--41 MHz frequency range and at 4.2 and 77.8 K. In this hexagonal crystal, the dynamic coupling between acoustic waves and the Re nuclear spin systems is shown to be via the dynamic quadrupole interaction, which is responsible for the observation of both {Delta}{ital m}={plus minus}1 and {plus minus}2 transitions between the {plus minus}3/2 energy levels and the mixed {plus minus}1/2 energy levels. Magnetic-resonance second moments for angular-independent indirect exchange broadening and angular-dependent static electric quadrupole broadening (from a spread in the electric quadrupole coupling constant value) are determined from the measured linewidths.