sodiumvapor

Sodium vapor refers to sodium atoms in the gaseous state, typically produced inside sealed discharge tubes or lamps. Sodium is a highly reactive alkali metal; it rapidly oxidizes in air and reacts vigorously with water, so pure sodium is stored under oil or in an inert atmosphere. In lighting devices, solid sodium is heated by an electric arc or other energy source, causing the metal to vaporize and sustain a discharge through the vapor.

The most characteristic feature of sodium vapor is its strong emission in the yellow region of the visible spectrum. The principal lines arise near 589.0 and 589.6 nanometers (the sodium D-lines). In low-pressure discharge tubes, these lines dominate the spectrum, yielding a nearly monochromatic yellow light. High-pressure sodium lamps emit a broader spectrum that includes a strong yellow component, with improved color rendering relative to the low-pressure variety.

Uses and applications include electric lighting and spectroscopic sources. The primary application of sodium vapor is lighting: low-pressure sodium lamps offer very high luminous efficacy and long life, but produce almost single-color light and poor color discrimination, limiting their use to exterior illumination. High-pressure sodium lamps provide higher intensity and warmer color performance, and are widely used for street and area lighting. Sodium vapor is also used in laboratory spectroscopy and calibration sources due to its well-defined spectral lines.

Safety and handling: sodium reacts violently with water and moisture; it is typically stored under oil or in an inert atmosphere. In lamp operation, the enclosed environment must be properly sealed to prevent reactions with oxygen or moisture.