ESTIMATION OF THE MOMENTUM TRANSFER CROSS SECTION FOR COLLISIONS OF ELECTRONS WITH IODINE ATOMS FOR THE MODELING OF HIGH PRESSURE METAL HALIDE LAMPS

摘要

The electrical conductivity of the plasma has an important impact on the temperature profile in the center of the plasma column of metal halide lamps. The reason for this is that in this arc region the ohmic heating which is determined by the electrical conductivity is balanced by the radiation release. The parameters needed for calculating the electrical conductivity are the electron density and the densities of the main collision partners of the electrons as well as the corresponding momentum transfer cross sections. In usual high pressure metal halide lamps the plasma component with the highest density is mercury. Its momentum transfer cross section is well known for the modeling of high pressure lamps. Iodine gets into the plasma by TlI, NaI and the rare earth iodides which all are completely dissociated in the arc center. The density of iodine reaches the order of 1/10 of the density of mercury. Since its momentum transfer cross section is much less known, its influence on the electrical conductivity of metal halide lamps is investigated in this work.