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Spectrochemical Instrumentation Modules

Spectrochemical Instrumentation Modules. 1. Light Source 2. Optical Components 3. Sampling Device 4. Wavelength Selector 5. Detector 6. Signal Processor. Spectrochemical Instrumentation Modules. Spectroscopic Light Sources. 1. Continuum Sources 2. Line Sources

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Spectrochemical Instrumentation Modules

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  1. Spectrochemical Instrumentation Modules 1. Light Source 2. Optical Components 3. Sampling Device 4. Wavelength Selector 5. Detector 6. Signal Processor

  2. Spectrochemical Instrumentation Modules

  3. Spectroscopic Light Sources 1. Continuum Sources 2. Line Sources 3. Quasi-continuum Sources

  4. Source Types

  5. Source Characteristics

  6. Continuum Sources Emit radiation over a broad spectral range. Continuum in Wavelength, not necessarily in time. Most of these are “black body emitters. The spectral range depends upon the temperature of the black body.

  7. Spectral Radiance of a Black Body

  8. Continuum Sources

  9. Continuum Sources

  10. Nernst Glower

  11. Globars

  12. Tungsten Lamps

  13. Hydrogen or Deuterium Lamp • Current through low pressure H2 or D2 • Fused silica window • 160-400 nm

  14. Xenon Lamps • Pass current through high pressure Xenon Gas • 200-1000 nm output, sapphire window • Provide high intensity, but with high noise

  15. Line Sources Emit intense radiation over a narrow spectral range (or line). The Full Width at Half Maximum (FWHM) for these sources is: FWHM ≤ 0.01 nm

  16. Typical of Line Sources 1. Low pressure pen lamps (Hg pen lamp) 2. Hollow Cathode Lamp (HCL) 3. Electrode-less Discharge Lamp (EDL)

  17. Pen Lamps • Low pressure metal vapor inside an electrical discharge • Spectra characteristic of the metal vapor • Often used for calibration purposes

  18. Hg Calibration Spectrum

  19. Hollow Cathode Lamps • Cylindrical Cathode containing metal of interest • Low pressure inert gas atmosphere • Produces spectrum of cathode metal

  20. Hollow Cathode Lamp Spectrum

  21. Electrode Discharge Lamps • Metal salt in inert atmosphere • Atomized and excited by RF field • 10 x stronger than HCL for volatile metals

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