EXPERIMENTAL-EVIDENCE FOR ROTATED TETRAHEDRA AS TUNNELING STATES IN NEUTRON-IRRADIATED QUARTZ

Ultrasonic attenuation measurements are carried out in neutron-irradia ted z-cut quartz and are analyzed in the framework of the tunneling mo del. It was previously derived that the coupling between the tunneling states and the longitudinal phonons behaves anisotropically. The obse rved increase in the anisotropy with the dose is explained in this pap er in terms of the relative contribution of the tunneling states in th e 'crystalline' and 'amorphous' part of the samples.