Spectroscopic Studies of Ionization in a Hollow-Cathode Discharge

The influence of carrier gas, carrier gas pressure, cathode geometry, and discharge current on the ionization of metal atoms in a hollow-cathode discharge was studied in some detail. Most of these studies were made with an iron hollow-cathode discharge. A measure of ionization was obtained from the intensity ratio of a line of the second to a line of the first spectrum. In general, this ratio was found to increase with carrier gas pressure and discharge current. This ratio also increased with increasing cathode bore diameter but decreased with increasing bore length. This ratio for iron was greatly affected by the use of different inert carrier gases. Of the five common inert gases used, xenon produced the largest value for this ratio and argon produced the smallest. The results of these studies indicated this may be a new method for distinguishing between lines emitted by the neutral atom and lines of the singly ionized atom.