Spectra of xenon and krypton arcs

The arc emission spectra of two identical high-pressure dc capillary lamps (one with 2 atmospheres xenon, one with 2 atmospheres krypton) are measured and compared. The total efficiency, as measured by a thermopile, approaches 55 percent for xenon as compared to 35 percent for krypton. The presence in the krypton spectrum of strong lines in the infrared proximate to the absorption bands of neodymium lasers accounts for such arcs being more efficient pump sources in such applications.