In the course of studies on the nuclear quadrupole resonance of iodine many absorption lines different from those of the nuclear quadrupole resonance have been found. After those investigations, similar absotption lines were found in piezoeleetric substances such as quartz crystal ahd Roehelle salt. These new found absorption lines were called piezoelectric lines, and the natures of these lines, were investigated by the Japanese researchers and a suggestion on the mechanism was also postulated.
Piezoelectric single crystals are well known to give many absorption lines due to harmonics of the natural vibration, and these lines are also well known to decrease regularly their intensities of absotption lines with increasing harmonics order. However the above mentioned piezoelectric lines always spread in the wide ranges of the frequency with almost constant intensities.
In this investigations, the lines of the piezoelectric absorption of single ctystals of Rochelle salt and quartz were observed in the frequency ranges from 18MHz to 34 MHz, and at least the presence of one series of new equidistant lines were clearly recognized in the spectrum of quartz.