The Opacity of an Ionised Gas

Abstract

IN a paper read before a joint meeting of the American Physical Society and the American Astronomical Society, in December, I pointed out that theoretically the absorption of radiation by free electrons should render an ionised gas highly opaque. The organised vibrational energy, due to the radiation, of the free electrons is transformed by collisions into disorganised thermal energy of translation. A tentative application of the methods of the well-known free electron theory of the optical properties of metals to conditions in an ionised gas gives the following equation for the volume opacity coefficient K. The quantity K is such that in distance z centimetres through the gas the intensity of the direct beam is reduced to e^Kz of its initial value.