INDUCED CHANGES IN THE DISTRIBUTION OF THE TUNNELING STATES

Ultrasonic attenuation measurements in neutron-irradiated quartz show distinct changes upon heat treatment in the behavior at the so-called plateau region. Since this plateau, observed in glasses and defective crystals such as neutron-irradiated quartz, is attributed to the specific distribution of the relaxation rates of the tunneling states (TS), the observations show that heat treatment can induce significant changes in this distribution, which provides an interesting tool to get more information about the nature of the tunneling states. The analysis in the framework of the tunneling model gives evidence that the TS with long relaxation times vanish upon heat treatment, which can be interpreted in terms of the disappearance of tunneling states with large mass. © 1995 The American Physical Society.