Important Atomic, Molecular and Radiative Processes in Low Pressure Discharge Lamps

Abstract

Low pressure discharges are used in a number of light sources, of which the most important application for general lighting is the fluorescent lamp (FL). In conventional FL, electrical energy is converted to UV radiation through excitation of mercury atoms; the UV is then converted to visible radiation using a phosphor. Other atomic radiators, such as sodium and rare gases, are used for applications but are unsuitable for general lighting. In recent years, there has been strong interest in finding alternative atomic and molecular radiators and research is continuing. The efficiency of producing light in a low pressure discharge depends on the balance between ionization processes, which sustain the plasma, and the excitation of atoms or molecules into radiating states through electron impact excitation and collisions between atoms in excited states. Since radiation emitted at one point in the discharge may be absorbed and re‐emitted several times before it finally reaches the wall, radiation transport also plays a significant role in determining the fraction of electrical energy which is converted to radiation. Numerical models can help guide the development of more efficient light sources, but there is currently a lack of data for a number of important fundamental processes. This paper will describe the important physical processes in low pressure discharge light sources, and discuss the requirements for new and improved atomic and molecular data.