A simple, completely sealed, discharge resonance lamp operated by a 2450 Mc/sec microwave power is described which emits atomic lines of sufficient intensity to be useful as a photochemical light source. When a water impurity is present in the lamp, many emission lines appear in the region of wavelength from 1500 to 2000 Å. These impurity lines can be effectively removed by means of a getter or by a suitable cold trap. The pressures of pure Xe or Kr in the resonance lamp, required to give maximum intensity (approximately 5× 1014 quanta/sec), are 0.7 and 1.0 mm, respectively. The presence of a CO impurity does not affect the intensity of the resonance lines. After passing through a 1-mm LiF window, the intensity of the Xe resonance line at 1295 Å is about 2% of that at 1470 Å and the intensity of the Kr line at 1165 Å is about 28% of that at 1236Å . A mixture of the rare gas and He gives more intense light than the pure gas. The lifetime of the rare-gas resonance lamps is approximately 10 h. Lyman alpha (1216 Å) line from excited atomic hydrogen and a group of lines at 1743–45 Å from excited atomic nitrogen may be used as a photochemical light source.
HIDEO OKABE, "Intense Resonance Line Sources for Photochemical Work in the Vacuum Ultraviolet Region," J. Opt. Soc. Am. 54, 478-481 (1964)