PURPOSE: To show the emission and absorption line spectrum for high pressure sodium gas.
DESCRIPTION:
A high pressure Na lamp shows the absorption line in the middle of the smeared emission line. See image above.
There are emission lines in addition to the Na due to the presence of Hg. Also, the Na emission line is not a simple line and is not the same as a low pressure Na emission line. The line is doppler broadened from pressure and thermally broadened from heat. Also, there is a temperature gradient inside the lamp. The gradient causes the Na gas at the outer wall of the lamp to cool and absorb light. The Na gas in the center of the lamp is hot and emits light. Thus the spectrum shows both emission and absorption simultaneously. It takes about four minutes for the lamp to warm up fully.
EQUIPMENT: Sodium lamp, grating, slit camera.
SETUP NOTES:
High Pressure Sodium Lamp
Updated by JZ in 3/07/2007