Intense Resonance Line Sources for Photochemical Work in the Vacuum Ultraviolet Region

TLDR

A sealed microwave‑driven discharge lamp emits intense atomic lines suitable for vacuum‑ultraviolet photochemistry, with water impurities producing additional 1500–2000 Å emissions and a typical 10‑hour lifetime, while Lyman‑α and nitrogen lines also serve as light sources. Impurity lines are removed by getters or cold traps, optimal Xe and Kr pressures (0.7 mm and 1.0 mm) yield ~5×10^14 quanta s^–1, CO does not alter intensity, and after a 1‑mm LiF window the Xe 1295 Å and Kr 1165 Å lines drop to 2 % and 28 %.

Abstract

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 1236 Å. 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.