Appearance resonance lamp

Resonance Lamp.—Such lamps (sometimes called low pressure lamps) are often used as line sources in photochemical studies. These usually contain a small amount of a metal vapor (e.g., mercury, cadmium, zinc, etc.) and several mm pressure of a rare gas. They operate at relatively low current (ca. 100 ma.) and high voltages (several thousand volts). This is in contrast to a typical medium pressure lamp which may operate off a 110-220 v. power supply delivering ca. 3-5 amp. The most common example in photochemistry is the mercury resonance lamp which has strong emission of the unreversed resonance lines at 2537 A. and 1849 A. (ca. 90% or more of the total) along with other, much weaker lines ( resonance lines are those which appear both in absorption and emission). There is little continuum. Sources of this type are widely used for photosensitized reactions. 

Nature of Ion Injected into Liquid Isobutylene. The krypton resonance lamp emits photons at 1236 A. (10.0 e.v.) and 1165 A. (10.6 e.v.) with relative intensities of 1.00 and 0.28 respectively (5). The ionization potential of isobutylene is 9.4 e.v., and the lowest appearance potential for a fragment ion from isobutylene is 11.3 e.v. (C4H7+) (I). Therefore, the only ion produced is the parent C4H8+. 

In Figure 1, the principle of atomic absorption is shown. The simplest possible system to carry out this principle appears in Figure 5. Light from the hollow-cathode lamp passes through the flame, after which the resonance wavelength is isolated by a monochromator or filter, and... 

Although many methods have been used to establish the temperature of a flame, the most widely accepted technique is the line reversal method. The flame is heavily doped with an element, usually sodium, which has a conveniently placed and easily excited resonance line. This resonance line is then viewed by spectroscope against the continuous background of a lamp, whose operating temperature is adjusted until the resonance lines disappear. If the flame is hotter than the lamp, the lines appear in emission (bright) while if the lamp is the hotter, the lines appear in absorption (dark). When the lines are not visible, the lamp and flame are believed to be at the same temperature. The temperature of the lamp filament is then measured independently with a pyrometer. The technique is discussed in detail, and the necessary precautions are outlined by Wolfhard and Gaydon or Lawton and Weinberg. ... 

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