Spectroscopy Discharge Tubes

Mercury Vapour Discharge Tubes


Mercury vaapour tubes generally also contain Argon, this being necessary to get the tube to strike and warm-up. In that case, the spectrum seen will exhibit peaks due to both elements. Generally, the peaks of wavelength <600nm are due to Hg, and the peaks of >600nm are due to Ar. The principal spectral lines for Hg and Ar are listed in the Ocean Optics calibration source documentation (see links below) and are as follows:

Hg (UV <390nm): 253.65, 296.73, 302.15, 313.16, 334.15, 365.01.

Hg (Visible): 404.66, 407.78, 435.84, 546.08, 576.96, 579.07.

Ar (IR > 600nm): 696.54, 706.72, 710.75, 727.29 738.40, 750.39, 763.51,

772.40, 794.82, 800.62, 811.53, 826.45, 842.46, 852.14, 866.79, 912.30 922.45.

The Hg lines at 436 and 546nm are used for calibration of the Theremino spectrometer.
The UV lines will be weak or absent in the presence of a glass outer envelope or an acrylic shield. The operation of unshielded silica-glass tubes requires protective clothing and eyewear.


>> Hg Spectrum Tube
>> Hg:Ar Sign tube
>> PJ Hg tube. Fill gas is 75% Ar 25% Ne.
>> Ar spectrum for comparison.
>> Ne spectrum for comparison.


Siemens Sieray 30mA HFAC
Sieray Hg lamp, HF AC Spectrum of Siemens Sieray high-pressure Hg lamp operated from a 30mA high-frequency signage ("neon tube") inverter-type power supply. The Sieray was used for street lighting, and has an outer glass envelope to capture UV.







Hg Hanovia Home Sin 30mA boro
Hanovia HomeSun "Sun Ray" lamp of late 1930s vintage. This has a fused silica-glass envelope, and was used without filtration on the basis that it could produce a sun tan. Users had to wear green goggles in order to avoid developing cataracts. Here the tube is operated from a 30mA high-frequency signage inverter and placed inside a borosilicate tube to prevent the strong UV emission at 254nm from causing harm.


>> white fluorescent tube (CFL)
>> insect attractor tube
>> blacklight tube


Ocean Optics HG-1 Hg:Ar calibration source documentation:
Ocean Optics HG-1 Hg:Ar Calibration Source.
HG-1 Hg:Ar Calibration Source Instructions.

Discharge Tubes