Ultrasonic Absorption in JRQ Samples 7.2,11.6 and 12.5

The ultrasonic absorption in the three JRQ samples designated 7.2, 11.6 and 12.5 has been determined by observing the decay of reverberation fields generated by short laser pulses. For detection a laser interferometer was used. This laser-ultrasonic method allows the direct measurement of the absorption in the material and since it is a non-contact technique no additional damping due to coupling losses play a role. The absorption was measured for different frequencies in a range from 299 kHz to 1 MHz at room temperature. The absorption exhibits the signes of an hysteretic absorption mechanism.