Spectra of Gas Discharges

Color spectra of elements undergoing electrical discharge excitation.

Hydrogen

Helium

Oxygen

Carbon

Nitrogen

Neon

Magnesium

Silicon

Sulfur

Iron

Aluminum

Calcium

Argon

Sodium

Krypton

Xenon

JPEG screen grabs of an applet which computes and plots the spectra in a web browser window. The above images aren't dithered. They may appear so if your display doesn't have enough colors to represent the entire color range. Displays limited to 256 colors or less don't produce acceptable spectra. Try increasing your color resolution to 16 or 24 bits (16 million colors).

This Java program reads a file containing a list of emission line wavelengths and their corresponding strengths then simulates the appearance of the spectrum in a good visual spectroscope.

Note: This program generates deep 24 bit color plots, therefore you may need to increase the color depth of your system to view subtle details in these spectra.

Warning: There may be a small delay as the Applet loads it's element emission line file and computes the spectra...

Click on an element name in the first column of the table below to launch the spectra viewer
If you prefer not to run the Applet click corresponding JPG in the next to last column to obtain an image.

Most common elements in solar spectrum. (listed in order of decreasing abundance)
Atomic No.	Element	Symbol	Data File	Emission Lines 4000-7000 Å	Jpeg Image	Original Data
1	Hydrogen	H	hydrogen.txt	5	JPEG	hydrogen.dat.gz
2	Helium	He	helium.txt	23	JPEG	helium.dat.gz
8	Oxygen	O	oxygen.txt	73	JPEG	oxygen.dat.gz
6	Carbon	C	carbon.txt	27	JPEG	carbon.dat.gz
7	Nitrogen	N	nitrogen.txt	84	JPEG	nitrogen.dat.gz
10	Neon	Ne	neon.txt	75	JPEG	neon.dat.gz
12	Magnesium	Mg	magnesium.txt	54	JPEG	magnesium.dat.gz
14	Silicon	Si	silicon.txt	109	JPEG	silicon.dat.gz
16	Sulfur	S	sulfur.txt	39	JPEG	sulfur.dat.gz
26	Iron	Fe	iron.txt	235	JPEG	iron.dat.gz
11	Aluminum	Al	aluminum.txt	38	JPEG	aluminum.dat.gz
20	Calcium	Ca	calcium.txt	78	JPEG	calcium.dat.gz
18	Argon	Ar	argon.txt	159	JPEG	argon.dat.gz
11	Sodium	Na	sodium.txt	90	JPEG	sodium.dat.gz
36	Krypton	Kr	krypton.txt	75	JPEG	krypton.dat.gz
54	Xenon	Xe	xenon.txt	139	JPEG	xenon.dat.gz
All Spectra		High Resolution 784 X 64			JPEG	catalog.dat.gz 306 KBytes

Atomic Number	The number of protons in the nucleus of the element.
Element	Click on the name in this column to launch the Applet which displays an emission line spectrum of the corresponding element
Symbol	Symbol from the table of the elements
Data File	Click on the name to download a text file containing an a list of emission lines in Ångstroms and their associated strengths for the corresponding element
Emission Lines 4000-7000 Å	Number of tabulated emission lines in the visible wavelength range
Jpeg Image	JPEG screen grab (784 X 8). The narrow height is to reduce transmission time, it expands to 64 pixels using HEIGHT=64 option in IMG tag of HTML file. To use images outside the context of a web browser, you should expand them vertically with image processor.
Original Data	Spectra of neutral and singly ionized elements from the Astronomical Data Center (ADC) catalog A6016, by Reader J., Corliss Ch.H. :1981, 'Line Spectra of the Elements', CRC Handbook of Chemistry and Physics; NSRDS-NBS 68

The element, wavelength range and line width are all controlled by applet parameter (PARAM) tags in the HTML source for this page. There are other options such as width and height of spectra in pixels and contrast which can also be controlled. There are also options to overlay a continuous blackbody spectrum of varying strength and to limit the wavelength range.
For example here are the parameters for Neon :

<APPLET CODE=discharge.class WIDTH=784 HEIGHT=64>
<PARAM NAME=element VALUE=neon.txt>
<PARAM NAME=startWavelength VALUE=4000>
<PARAM NAME=endWavelength VALUE=7000>
<PARAM NAME=lineWidth VALUE=2.5>
<PARAM NAME=contrast VALUE=10>
<PARAM NAME=continuum VALUE=0.3>
</APPLET>

The simulated gas discharge spectrum is synthesized by assigning each emission line to a gaussian and each point in the spectra is computed as a mathematical sum of all the emission lines.

Contrast:
- Range: 1 to 10000 (the upper limit comes from intensity of the weakest line)
- Default: 1 (maximum of strongest line assigned to maximum intensity, no distortion of line profile)
- Should be adjusted to 'burn out' the strongest lines and boost the intensity of the weaker lines. Should not be too high or some line blending may occur, also the relative difference between the various emission line strengths is lost. A compromise should be reached.
Line Width:
- Range: 0 to 100
- Default: 3
- The width of emission lines is user controlled and should be adjusted so that the line profile covers at least one pixel; too small a width causes undersampling to occur and some lines may 'disappear'! However too broad a line will cause blending of lines that are closer together. Again, a compromise must be reached.
Continuum:
- Range: 0 to 1
- Default: 0.3
- Physics: In many plasma environments some residual broadband background light 'pollutes' the spectrum, either by scattering from an external white source or internal transitions involving the ion continuum. This causes a smooth background to appear as weak 'rainbow' below the level of most of the emission lines. This creates a 'pleasing' colored background which 'fills' in the empty gap between the emission lines.
This Applet was created by John Talbot
The data for these spectra is courtesy of the Astronomical Data Center, and the National Space Science Data Center through the World Data Center A for Rockets and Satellites.