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Laser-Based Aerosol Diagnostics

ENV 6130 Aerosol Mechanic. Laser-Based Aerosol Diagnostics. Jun Wang Mar 23 rd , 2010. Outline. Laser Background Theory and Instrumentation Summary References Is there any laser in your life?. Source: Xlaserbeam.com. Light. What is light

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Laser-Based Aerosol Diagnostics

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  1. ENV 6130 Aerosol Mechanic Laser-Based Aerosol Diagnostics Jun Wang Mar 23rd, 2010

  2. Outline • Laser Background • Theory and Instrumentation • Summary • References Is there any laser in your life? Source: Xlaserbeam.com Laser Based Aerosol Diagnostics

  3. Light • What is light • Electromagnetic radiation of specific wavelength (nm) • Properties: Intensity, frequency, polarization, phase, speed, and etc. • Basic Unit: Photon • Photon Energy E Max Planck (1858~1947) Source: Wikipedia Laser Based Aerosol Diagnostics

  4. Light Light Spectrum Source: SVGbot Laser Based Aerosol Diagnostics

  5. Light Optics • Interaction between light and matter Spontaneous or Stimulated Emission Laser Based Aerosol Diagnostics

  6. Laser • L. A. S. E. R. • Light Amplification • by Stimulated • Emission of Radiation Laser Based Aerosol Diagnostics

  7. Type of Laser • By Mode • Continuous Wave (CW) Laser • Pulsed Laser • By Medium • Gas Laser ( He:Ne, CO2, Ar:Ion ) • Chemical Laser • Excimer Laser • Solid-State Laser ( Nd: YAG ) • Dye Laser Laser Based Aerosol Diagnostics

  8. Laser Diagnostics Elastic • Light Scattering ( Rayleigh/Mie ) • Raman ( Vibrational /Rotational ) • Fluorescence • Laser induced Plasma/Laser induced Breakdown Inelastic Laser Destructive Vs Non-Destructive Aerosol Laser Based Aerosol Diagnostics

  9. What can be measured? • Indentify unknown chemical species of aerosol • (Peaks at finger print wavelength, Library/Ref) • Examine changes in aerosol evolution • Chemical ( bond alteration ) • Physical ( phase, stress ) • Absorbed materials/contaminant on aerosol • Quantify concentration (size/number density) • Surface Temperature of Aerosol • Remote Sensing of bulk aerosols Laser Based Aerosol Diagnostics

  10. Light Scattering (Rayleigh/Mie) • Redirection of EM wave when encounters an obstacle or non-homogeneity (Scattering Aerosol). • It is NOT a simple bounce of Photon. Hahn, D. W. et al Laser Based Aerosol Diagnostics

  11. Light Scattering (Rayleigh/Mie) • Rayleigh Theory • Small, dielectric, non-absorbing, spherical. • Mie Theory • Spherical, absorbing/non-absorbing, no size bound. Lord Rayleigh Gustav Mie Source: Nobelprize.org Laser Based Aerosol Diagnostics

  12. Light Scattering (Rayleigh/Mie) • Parameters in Rayleigh/Mie Scattering • Criteria for Rayleigh Regime α<<1, or |m| α<<1 Laser Based Aerosol Diagnostics

  13. Light Scattering (Rayleigh/Mie) • Parameters in Rayleigh/Mie Scattering Laser Based Aerosol Diagnostics Hahn, D. W. et al

  14. Light Scattering (Rayleigh/Mie) Intensities of scattering radiation Scattering Cross Section ( σ, cm2/sr ) Laser Based Aerosol Diagnostics

  15. Light Scattering (Rayleigh/Mie) • Rate of Scattering energy into a defined angle Hahn, D. W. et al Laser Based Aerosol Diagnostics

  16. Light Scattering (Rayleigh/Mie) • Rayleigh Theory • Differential Scattering Cross Sections Why our sky are BLUE? Laser Based Aerosol Diagnostics

  17. Light Scattering (Rayleigh/Mie) • Implication • Unpolarized light will be strongly polarized at 90o observation for Rayleigh Particles. • Extinction = absorption (α3) + scattering (α6) Laser Based Aerosol Diagnostics

  18. Light Scattering (Rayleigh/Mie) • Mie Theory • Differential Scattering Cross Sections Averaged Laser Based Aerosol Diagnostics

  19. Light Scattering (Rayleigh/Mie) • Mie theory Laser Based Aerosol Diagnostics

  20. Raman / Vibrational Mode • Dipole Moment • Induced by interaction between EM wave and aerosol • Depends on polarizability of molecule Laser Based Aerosol Diagnostics

  21. Raman / Vibrational Mode Laser Based Aerosol Diagnostics

  22. Raman / Vibrational Mode • Induced dipole moment will be created at Vo, Vo+Vvib, Vo-Vvib Laser Based Aerosol Diagnostics

  23. Raman / Vibrational Mode • Polarizability of A-B as a function of vibrational displacement. Laser Based Aerosol Diagnostics

  24. Raman / Vibrational Mode Vibrational Energy Well Stokes Shift Laser Based Aerosol Diagnostics

  25. Raman / Vibrational Mode • First person to describe inelastic scattering C. V. Raman Raman Scattering Laser Based Aerosol Diagnostics

  26. Raman / Vibrational Mode • Raman Spectroscopy • Raman signal is weaker than elastic scattering signal on several orders. • E.g. N2, • For solid, the difference is more. Laser Based Aerosol Diagnostics

  27. Raman / Vibrational Mode • Raman differential scattering cross-section e.g. N2 Vvib = 2331 cm-1 @ 488nm excitation laser @ 632nm excitation laser How you select the excitation wavelength? 5.5 x 10-31 cm2/sr 1.7 x 10-31 cm2/sr Laser Based Aerosol Diagnostics

  28. Raman / Vibrational Mode • Select Rule of Raman Excitation Wavelength • Raman scattering cross-section • Magnitude of Raman shift in wavelength • Potential of interference by fluorescence • Avoid Interference Signals • Saturation of Fluorescence Signal • Amplification of Raman Signal • Czerny-Turner Box • Filters (Natch Filter/ Razor Edge Filter) • Measure Anti-Stokes Laser Based Aerosol Diagnostics

  29. Amplification of Raman Signal • Surface Enhanced Raman Scattering (SERS) • Electron oscillation induced by induced EM fields by conduction bonds of metals. • Enhance of Raman signal by Plasmon provided by metal surface. (1011~1015) • Metal only • Detect surface of aerosol • Detect biomaterials by implant metal nanoparticles Laser Based Aerosol Diagnostics

  30. Example of Raman Shift Hahn, D. W. et al Laser Based Aerosol Diagnostics

  31. Example of Raman Shift Hahn, D. W. et al Laser Based Aerosol Diagnostics

  32. Example of Raman Shift Hahn, D. W. et al Laser Based Aerosol Diagnostics

  33. Raman / Rotational Mode • Rotational transitions of the molecules when scattering • Favorable Two-Photon Process • J ~ Rotational Quantum Number Laser Based Aerosol Diagnostics

  34. Raman / Rotational Mode A Typical Raman Scattering Spectrum (Bulatov, V et al) Laser Based Aerosol Diagnostics

  35. Raman / Rotational Mode e.g. HCl Laser Based Aerosol Diagnostics

  36. Raman / Rotational Mode • Rotational Raman Temperature Diagnostics • Find Jmax Laser Based Aerosol Diagnostics

  37. Fluorescence • Inelastic scattering process • Incident photon are absorbed • Undergo internal conversion • Re-emit photon at a longer wavelength • Notice: Multi photon absorption • Most organic and biological matters will under go fluorescence. • Fluorescence is most pronounced around 400nm. Laser Based Aerosol Diagnostics

  38. Fluorescence • Temporal difference between Raman and Fluorescence. • Raman: ‘Prompt’ • Fluorescence: Always Delayed Laser Based Aerosol Diagnostics

  39. Fluorescence • Laser-induced Fluorescence • Great sensitivity, low background, possible to distinguish more species. • Structure of molecules, selective species. • Depending on what is tuned • Disperse Spectra • Excitation Spectra Laser Based Aerosol Diagnostics

  40. LIPS/LIBS • Laser induced plasma spectroscopy (LIPS) • Do not need chemical digestion Neuhauser, R. E, et al Laser Based Aerosol Diagnostics

  41. LIPS/LIBS • Selective of filters • Sufficient temperature resistance • Low background concentration • Sampling efficiency • Data Analysis of LIPS/LIBS • Fit the emission line to Gaussian Profile. Laser Based Aerosol Diagnostics

  42. LIPS/LIBS Panne U., et al Laser Based Aerosol Diagnostics

  43. LIPS/LIBS • Metal Element Analysis Panne U., et al Laser Based Aerosol Diagnostics

  44. Summary • Advantage of Laser Based Aerosol Diagnostics • Intense, collimated, coherent, monochromatic light • Short response time, mostly online • Highly spatial resolutions • Solids, liquids, and gases • Non-destruction in some case • Disadvantage of Laser Based Aerosol Diagnostics • High cost • Saturation and matrix effect Laser Based Aerosol Diagnostics

  45. References • Hahn, D. W., EGM 6006 Course in University of Florida, Spring 2010 • Rosen, L. C.; Ipser, J. Atmospheric Environment. Part A. General Topics 1991, 25, 2643-2651. • Neuhauser, R. E.; Panne, U.; Niessner, R.; Petrucci, G. A.; Cavalli, P.; Omenetto, N. Analytica Chimica Acta 1997, 346, 37-48. • Neuhauser, R. E.; Panne, U.; Niessner, R.; Steinicke, W. H.; Grimm, H. J. Journal of Aerosol Science 1997, 28, S437-S438. • Zhaozhu, G. E.; Wexler, A. S.; Johnston, M. V. Journal of Aerosol Science 1998, 29, S1193-S1194. • Neuhauser, R. E.; Panne, U.; Niessner, R. Analytica Chimica Acta 1999, 392, 47-54. • Sandsten, J.; Gustafsson, U.; Somesfalean, G. Optics Communications 1999, 168, 17-24. • Carranza, J. E.; Fisher, B. T.; Yoder, G. D.; Hahn, D. W. Spectrochimica Acta Part B: Atomic Spectroscopy 2001, 56, 851-864. • Litani-Barzilai, I.; Fisher, M.; Gridin, V. V.; Schechter, I. Analytica Chimica Acta 2001, 439, 1-8. • Panne, U.; Neuhauser, R. E.; Theisen, M.; Fink, H.; Niessner, R. Spectrochimica Acta Part B: Atomic Spectroscopy 2001, 56, 839-850. • Bulatov, V.; Fisher, M.; Schechter, I. Analytica Chimica Acta 2002, 466, 1-9. • de Boer, A. H.; Gjaltema, D.; Hagedoorn, P.; Frijlink, H. W. International Journal of Pharmaceutics 2002, 249, 219-231. • Diwakar, P. K.; Jackson, P. B.; Hahn, D. W. Spectrochimica Acta Part B: Atomic Spectroscopy 2007, 62, 1466-1474. • Diwakar, P. K.; Jackson, P. B.; Hahn, D. W. Spectrochimica Acta Part B: Atomic Spectroscopy 2007, 62, 1466-1474. • Asgill, M. E.; Hahn, D. W. Spectrochimica Acta Part B: Atomic Spectroscopy 2009, 64, 1153-1158. Laser Based Aerosol Diagnostics

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