Model 625 Mercury (Hg) Wavelength Calibration Line Source
Narrow Discrete Spectral Lines
Excellent Stability
Long Life
Fits directly to most McPherson slit assemblies

Mercury calibration lamps are small, rugged, and convenient to use. The lamps contain a small amount of Mercury and a fill gas, usually Argon or Neon. The Mercury emission lines dominate the output spectrum. Because the lamps operate at low pressure, the spectral lines in the output are sharp and separate. The background between the lines is very low. The output wavelengths are known exactly and lamps are ideal for spectral calibration and as line sources. Single lines are easily isolated with optical filters for alignment and irradiation. Closely spaced lines are very useful for testing the resolution of dispersive instruments.
Model 625 Mercury pen type lamp in mounting flange

Mercury spectral calibration lamps make excellent high intensity short wave UV sources. About 90% of the total output is in the 253.7 nm line when the lamps are run at 18 mA. Therefore, appropriate UV eye safety measures are required. With an 18 mA power supply, the spectral output is dominated by ultraviolet Mercury emission lines. The visible lines are intense enough to be useful for calibration of McPherson monochromators. For higher mercury line intensity in the visible, a 25 mA power supply is necessary to shift power from the 253.7 nm line to the visible lines. As a result of the higher current, only 30% of the original output at 18 mA is left in the 253.7 line. Lamp life is reduced slightly from more than 5000 hours to around 4500 hours with the higher current.

Mercury-Neon (Hg-Ne) Lamps - The Hg-Ne Lamp contains both mercury and neon and the lamp emission spectrum is temperature dependent. When the lamp is run at normal lab ambient temperature, the output is very similar to the Hg(Ar) Lamp, while forced air cooling of the lamp adds the neon lines to the output. This spectrum has a large number of useful calibration lines in the 330-360 nm and 530-760 nm regions. These lamps should be run with 18 mA power supplies and lamp life is about 500 hours.