Sodium Clusters for a Superior Light Source

Sodium lamp is one of the most efficient light sources operating at about 45% efficiency, nearly twice that of a fluorescent lamp. Yet it is used only in niche applications such as outdoor lighting, because of a number of shortcomings. The lamp emits predominantly in the yellow wavelengths of sodium vapor; therefore its color rendering capability is poor. Sodium in the lamp needs to be evaporated to a gas before it can emit light, which introduces several minutes of delay after the lamp is electrically turned on. Melting temperature of solid sodium is 98 degrees C; the lamp has to be operated at much higher temperatures for the vapor to achieve an optimal light emitting state. Sodium reacts vigorously with atmospheric gases like oxygen and water vapor, which poses a safety hazard in case of accidental breakage of the lamp. The objective of this research is to alleviate all of these shortcomings by redesigning the lamp such that sodium is utilized in the form of small clusters rather than as a vapor. Design issues include optical properties of the clusters, stability of the material and safe operation of the lamp.