Sodium Clusters for a Superior Light Source

H. Gokturk
Ecoken, US

Keywords: sodium clusters, optical properties, bonding energy


Sodium lamp is one of the most efficient light sources providing an output of 150-200 lumens/watt; for comparison, light output of a fluorescent lamp is about 60-100 lumens/watt. Despite its efficient operation, sodium lamp is used only in niche applications such as outdoor lighting, because of a number of shortcomings. The lamp emits predominantly in the characteristic yellow wavelengths of sodium (~589 nm); therefore its color rendering capability is poor. Sodium in the lamp needs to be evaporated to a vapor before it can emit light, which introduces several minutes of delay after the lamp is electrically turned on. Melting temperature of sodium is ~98°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 hazard in case of accidental breakage of the lamp. The objective of this research is to alleviate 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.