On the concept of cyclotron resonance in metals

Experimental evidence is presented, indicating that an impinging, high frequency electromagnetic wave penetrates to a considerable depth beneath the surface of a monocrystalline, metallic sample. It is shown, on the basis of a rigorous dispersion equation for cyclotron waves, that the attenuation length for these waves is γ i = v g τ where v g is the group velocity and τ the relaxation time. The attenuation length varies in a characteristic way with the magnetic field and may become as large as the mean free path of the charge carriers. A possible relation to Azbel‐Kaner cyclotron resonance is pointed out.