Absorption and emission of copper radiation in a low and a high voltage internal anode hollow cathode discharge

The internal anode hollow cathode discharge (IAHCD) achieves positive current voltage behavior in a hollow cathode related construction by using the obstructed discharge phenomenon. A stronger current-voltage dependence is obtained by increasing the degree of obstruction or decreasing the fill gas pressure. Of the five noble gases He, Ne, Ar, Kr and Xe, Ne provides the highest intensity for the Cu I 324.7 nm emission in both a low and high voltage version of the IAHCD. The other four noble gases have increased Cu I 324.7 nm emission intensity relative to neon in the high voltage discharge. Atomic absorption measurements through the cathode bore indicate that at the pressure yielding the highest Cu I 324,7 nm emission for each gas and the same current for all investigated gases, the absorbance of the discharge increases with the atomic weight of the fill gas. The intensity of the Cu II 224.3 and 224.7 nm lines compared to the Cu I 324.7 nm line are greatest for Ar, Ne and He gases whose metastable or ion energies are greater or equal to the excitation energy of the ion lines. The ionic-atomic line intensity ratio is higher in the high voltage than the low voltage IAHCD.