Low Pressure Sodium Vapor Lamp provides light at 589 nm and 589.6nm, useful for wavelength calibration or resolution regulation.
When the lamp is turned on it emits a dim pink light to warm the sodium metal and then it turns into the common bright orange color as the sodium metal vaporizes.
Generally, Low-pressure sodium lamps require a warm up period of about ten minutes before it reaches substantially full light output, and have to cool before they can restart.