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Cu-Ar lamp

The Copper-Argon lamp presently in use with the IDS shows only ArI and ArII spectra. Copper lines are not seen. It shows two distinct spectral regions:

1. Between 3900 Å and 6965 Å the spectrum contains a large number of relatively faint lines, which can be used in both low and high dispersion work. The region 3900 Å to 5100 Å is particularly useful both with CCD and IPCS detectors. Between 5200 Å and 5500 Å , although there are a large number of lines, they are comparatively weak and large exposure times are needed. One may be better off with the Th-Ar lamp for this region.

2. Redwards of 6965 Å up to 9784 Å , the spectrum contains a large number of strong and very strong emission lines, which give the argon arc its characteristic red colour. However between these strong lines there are gaps devoid of even very weak lines, particularly redwards of 7500 Å . There the spectrum is only useful at low dispersion (150, 300 and 400 g/mm gratings) or at high dispersion, in combination with another lamp (e.g. Cu-Ne).