THE ABSORPTION OF RADIATION BY BALLISTIC ELECTRONS IN CONDUCTING DISKS

The absorption of electromagnetic radiation by small conducting discs is calculated for the case of ballistic electron motion, using a semic lassical analysis valid at frequencies small compared to the plasma fr equency omega(p). For a smooth walled disc there are complicated reson ance structures, and the absorption coefficient has a low-frequency cu t-off at a critical frequency omega(c), which corresponds to the frequ ency of a circumferential classical orbit of an electron at the Fermi surface. For frequencies satisfying omega(c) much less than omega much less than omega(p), the absorption coefficient is proportional to ome ga if fluctuations due to resonances are averaged over. We also consid er a rough-walled disc and some more general shapes: the proportionali ty to omega rather than the expected omega2 is a general feature.