On the Piezoelectric Lines at Sub-microwave Frequencies

Abstract

Piezoelectric absorption lines which had been found in the experiment of nuclear quadrupole resonance were studied in the frequency range between 3 Mc and 700 Mc. These lines were observed not only in powder, but also in single crystals. The present experiment showed that they were neither due to resonant vibrations of individual crystals in powder nor due to harmonics of the natural vibration of a single crystal. The absorption was dependent on imperfection of crystal and related to very narrow region in a crystal. The following mechanism was suggested: There are regions where the velocity of the elastic wave is smaller than the outside. Then vibrations are confined within the region because of total reflection at the boundary.