Resonance Absorption of Sunlight in Twilight Layers

Abstract

Solar radiation must pass at least once through the absorbing layer to reach the twilight zone of a layer of atoms scattering resonance radiation. The attenuation of the solar beam is calculated for resonance absorption and the resulting scattered intensity compared with the transparent layer model intensity for the same thickness of material. It is shown that in the case of sodium, the reduction in intensity for layers thicker than ${10}^9$ atoms/${\mathrm{cm}}^2$ is too serious to permit the deduction of layer thickness from a simple theory which neglects imprisonment of resonance radiation.