Spectra of Gas Discharges

Color spectra of elements undergoing electrical discharge excitation.








These image are lower quality jpeg screen grabs of an applet which computes an plots the spectra in a web browser window. 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...

Element Symbol Data File Emission Lines
4000-7000 Å
Neon Ne neon.txt 75 JPEG neon.dat.gz
Argon Ar argon.txt 159 JPEG argon.dat.gz
Krypton Kr krypton.txt 75 JPEG krypton.dat.gz
Nitrogen N nitrogen.txt 84 JPEG nitrogen.dat.gz
Xenon Xe xenon.txt 139 JPEG xenon.dat.gz
Helium He helium.txt 23 JPEG helium.dat.gz
Hydrogen H hydrogen.txt 5 JPEG hydrogen.dat.gz
All Spectra Medium Resolution 640 X 64 JPEG catalog.dat.gz
306 KBytes
All Spectra High Resolution 784 X 64 JPEG catalog.dat.gz
306 KBytes
If you system has enough resources you may be able to view All Spectra simultaneously by jumping to a web page with 7 concurrent spectra Applets running in low (640 X 64) or high (784 X 64) resolution

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 Screen grab in lossy JPEG image format (784 X 8). The jpegs have a narrow height to reduce transmission bandwidth, the width is expanded to 64 pixels using the HEIGHT=64 option in the IMG tag of the HTML file.
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>
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. This applet was successfully run under the following browsers : An upcoming version of this Applet will include a more graphical user interface for controlling these parameters.

This Applet was created by John Talbot. Source code is available : discharge.java

You can also download the source file, class file, these HTML pages and all the element data as :
discharge.zip (40 kBytes)

Physics Background

There are two basic line broadening mechanisms; instrumental and intrinsic : In most thin plasmas one sees a combination of Doppler and Lorenztian broadening called Voigt profiles. The Lorentzian component affects mostly the low intensity 'wings' of the emission lines so line profiles can be approximated as gaussians, especially considering the dynamic range limitations of computer screens. Most of the time spectra taken by researchers do not fully resolve the intrinsic line profile so the lines are broadened mainly by instrumental imperfection.

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.


Laser Stars