The Interaction of Microwave Phonons with Irradiation Centres in Quartz

The electron spin resonance spectrum of the paramagnetic centres produced by the X‐irradiation of quartz has been investigated at 1.8 °K at 10 GHz from well below to above the microwave saturation region. Hypersonics at 10 GHz were then introduced and this reduced the resonance signal. The effect has been studied as a function of hypersonic power and frequency, microwave monitoring power and magnetic field orientation. The experimental results suggest that the spin‐lattice relaxation time is of the order of 6 s at 1.8 °K and is determined by cross relaxation processes.