James E. Drummond

Smith-Purcell radiation in the high conductivity and plasma frequency limits

Radiation is calculated from currents produced by a nonrelativistic point charge that moves at a constant velocity above a conducting grating. Two different limits are considered. In the high conductivity limit, the surface charge is calculated from a nonretarded image charge, surface currents from the continuity equation, and the far field vector potential from the surface current. In the plasma frequency limit of the grating substrate a nonretarded electric potential is calculated from a two-region problem, bulk current from an interior potential, and the far field vector potential from the bulk current.

Van der Waals attraction between two conducting chains

Abstract The Van der Waals force between two conducting chains is shown from the zero point energies of the strongly spatially dispersive plasmon modes to vary at small separations L as L −3 instead of L −6 as for nonconducting chains.

PLASMA EFFECTS IN ANNULENE MOLECULES

Some plasma effects of the pi electrons in annulene molecules are studied. The dispersion relation for plasma oscillations, obtained by using Huckel molecular orbitals in the second quantization formalism, is found to describe soundlike waves. The resulting polarization response of the pi electrons causes a spatial modulation of the interaction potential between two pi electrons. The polarization response defines the natural correlation units in annulenes to be quartets in all but the angular momentum l = ± 2n states of 4n‐annulenes and zero angular momentum states, where the correlation unit is a pair of electrons. Correlation is discussed by using the modified interaction potential with a Wannier hamiltonian in pair and quartet equations. The effect of band alternation is considered in connection with the variation of induced currents in unsaturated annulenes with temperature.

Calculation of van der Waals forces in systems with nonlocal conductivity

A method is presented for calculating van der Waals forces in systems with nonlocal conductivity. The fluctuating fields in the electromagnetic stress tensor are obtained by applying the fluctuation‐dissipation theorem to the response of the system to an external polarization. As an example, the method is used to calculate the contribution of conduction electrons to the interaction of two blocks of metal. When the electrons are described in a simple hydrodynamic approximation keeping only the lowest order nonlocal terms, the interaction force is the same as that obtained by Lifshitz assuming local conductivity. At separations large compared to the London penetration depth c /ωp the interaction is due to electromagnetic waveguide modes, while at distances small compared to c /ωp, the force is due to surface plasmons. As a second example, the method is applied to the interaction of two graphitelike blocks. With a quantum mechanically derived description of the electron motion, the resulting force differs fr...