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Chapter 7

Chapter 7. Components of Optical Instruments. Components of Optical Instruments.

leslie-chang
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Chapter 7

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  1. Chapter 7 Components of Optical Instruments

  2. Components of Optical Instruments Typical spectroscopic instruments contain five components: (1) a stable source of radiant energy, (2) a transparent container for holding the sample, (3) a device that isolates a restricted region of the spectrum for measurement, (4) a radiation detector that converts radiant energy into a signal detector, (5) a signal processor and readout.

  3. Components of Optical Instruments • Absorption • Fluorescence • Phosphorescence • Scattering • Emission • Chemiluminescence

  4. Rayleigh & Raman Scattering • Occur when the dimensions of the particles that cause the scattering are small in comparison to the wavelength of the incident radiation. Dissolved particles can result in Rayleigh and Raman scattering. • A type of Raman Spectrometer: FRA 106/S Spectrometer

  5. Sources of Radiation Requirements • Sufficient power • Stability over long periods of time • Voltage regulation required as radiant power varies exponentially with voltage

  6. Lasers

  7. Lasers • Pumping • Spontaneous emission (fluorescence) • Stimulated emission • Absorption

  8. Wavelength Selectors Filters • Interference Filters • Interference Wedges • Absorption Filters

  9. Wavelength Selectors Monochromators- one color - pass a narrow band of wavelengths The SURE_SPECTRUM is an imaging spectrograph and scanning monochromator that features dual exit ports for maximum flexibility.

  10. Wavelength Selectors View of inside of monochromator

  11. Wavelength Selectors

  12. Radiation Transducers Photomultiplier

  13. Radiation Transducers Photodiode Arrays (PDA)

  14. Radiation Transducers Charge Transfer Devices • Charge Injection Devices (CID) • Charge-Coupled Devices (CCD)

  15. Signal Processors & Readouts Photon Counting Advantages: • Improved signal-to-noise ratio • Sensitivity to low radiation levels • Improved precision for a given measurement time • Lowered sensitivity to photomultiplier tube voltage and temperature fluctuations • Detection method of choice in fluorescence, chemiluminescence, and Raman spectrometry

  16. Signal Processors & Readouts Photon Counting Disadvantages: • Required equipment is more complex and expensive • Technique has not been widely applied for routine molecular absorption measurements in ultraviolet and visible regions

  17. Principles of Fourier Transform Optical Measurements • Transforms data set from time domain to frequency domain • Advantages • Throughput • High resolving power • Interferometers • Michelson • Mach-Zender • Fabry-Perot

  18. References • www.anachem.umu.se/jumpstation.htm • www.anachem.umu.se/cgi/jumpstation.exe?AtomicSpectroscopy • www.anachem.umu.se/cgi/jumpstation.exe?OpticalMolecularSpectroscopy • www.minyos.its.rmit.edu.au/~rcmfa/mstheory.html • http://science.widener.edu/sub/ftir/intro_it.html • http://www.s-a-s.org/ • http://www.chemsw.com • http://www.scimedia.com/chem-ed/spec/atomic/aa.html • http://www.chemistry.msu.edu/courses/cem333/Chapter%207%20-%20Components%20of%20Optical%20Instruments.pdf • http://www.brukeroptics.com/ • http://laxmi.nuc.ucla.edu:8248/M248_99/autorad/Scint/pmt.html • http://www.spectralproducts.com • http://www.parallax-tech.com/twotubes.htm • http://www.thespectroscopynet.com/Educational/Gratings.htm • http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/ebccd.html • http://www.cerncourier.com/main/article/43/2/7/1/cernnews9_3-03

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