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 3. Quasi-continuum Sources

Source Types

Source Characteristics

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.

Spectral Radiance of a Black Body

Continuum Sources

Continuum Sources

Nernst Glower

Globars

Tungsten Lamps

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

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

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

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

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

Hg Calibration Spectrum

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

Hollow Cathode Lamp Spectrum

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