History

Raman Scattering Technique in Thermal Fluid and Combustion Measurement

• This inelastic scattering process has been predicted by A.G. Smekal back in 1923 by his quantum theory of dispersion

Dr. Mazlan Abdul Wahid Faculty of Mechanical Engineering Universiti Teknologi Malaysia

• experimentally verified not earlier than 1928 by C.V. Raman in Calcutta

www.fkm.utm.my/~mazlan

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Thermal Fluid Measurement and Diagnostic MMJ 2413

• Raman spectroscopy is a light scattering technique, and can be thought of in its simplest form as a process where a photon of light interacts with a sample to produce scattered radiation of different wavelengths.

DR MAZLAN 2006

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Objective/Scope

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Origin of Raman

Raman scattering technique will be discussed. Discussion include introductory to raman scattering technique, basic experimental setup and application of Raman scattering technique in thermal fluid and combustion measurement.

Light scattered from a molecule has several components - the Rayleigh scatter and the Stokes and Anti-stokes Raman scatter.

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Scattered Light 1  ∂α   qo Eo [cos{2π (vo + vm )t} + cos{2π (vo − vm )t}] P = α o Eo cos(2πvot ) +  2  ∂q  0

Where; P = electric dipole moment α = proportionality constant called polarizability αo = polarizability at the equilibrium position vo = incident beam frequency vm = vibrational frequency q0 = vibrational amplitude of nuclear displacement t = time Eo = vibrational amplitude of the electric field strength

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Energy Diagram for Raman Scattering

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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INSTRUMENTATION AND EXPERIMENTAL TECHNIQUES

Five major components : 1) Excitation source 2) Sample illumination and scattered light collection system 3) Sample holder 4) Monochromator or spectrograph 5) Detection system, consisting of a detector, an amplifier and an output device. Figure: Schematic diagram of a typical dispersive Raman system. (John R. Ferraro,1994) FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Excitation Sources

• Since Raman scattering is inherently weak, the laser beam must be properly focused onto the sample, and the scattered radiation efficiently collected

Schematic of a typical gas laser (John R. Ferraro,1994).

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Sample illumination

Continuous wave (CW) lasers such as Ar+(351.1-514.5nm), Kr+(337.4-676.4nm) and He-Ne(632.8nm) are commonly used for Raman specyroscopy. More recently, pulsed lasers such as Nd:YAG, diode, and excimer lasers have been used for time resolved and UV resonance Raman spectroscopy.

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Thermal Fluid Measurement and Diagnostic MMJ 2413

Configurations for (a) 90º scattering and (b) 180º scattering (John R. Ferraro,1994). DR MAZLAN 2006

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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The monochromator Schematic of Spex Model 1403/4 double monochromator (John R. Ferraro,1994).

• Single monochromator - extraneous light that bounces around the spectrometer overlaps the weak Raman scattered light. This is caused mainly by undiffracted light scattered from the face of the grating. • Such stray light could be reduced considerably by arranging two/three spectrometers in tandem so that the output of one was purified by the second. • Recently, high performance Raman systems have been built by combining a single-stage spectrograph, charge-coupled device (CCD) detectors, and several kinds of filters that reject Rayleigh scattering efficiently FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Schematic of Soex Model 1877 triple monochromator. The exit slit is removed for multichannel detection. (John R. Ferraro,1994).

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Detection system • Since Raman signals are inherently weak, the problems involved with detection and amplification are severe. • Several detection techniques are, (John R. Ferraro, 1994): » Photon Counting » Photodiode Array Detection » Charge-Coupled Device (CCD) Detection System

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Schematic of a head-on type photomultiplier (PM) tube(John R. Ferraro,1994).

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(a) Schematic of a photodiode array detector. (b) Schematic of a CCD detector. (John R. Thermal Fluid MeasurementFerraro,1994). and Diagnostic MMJ 2413 DR MAZLAN 2006

Instrument Calibration

Sampling Techniques

• Frequency Calibration – Internal Standard – Indene – Laser Plasma Lines – Neon Emission Lines • Intensity Calibration Relative intensity of Raman band I = constant x concentration, C rel

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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(a) Gas cell with external resonating mirrors. (b) Capillary cell for liquids (c) Cylindrical cell for liquids. (d) KBr pellet for solid samples(John R. FKM UTM Thermal Fluid Measurement and Diagnostic MMJ 2413 DR MAZLAN 2006 Ferraro,1994).

Special Techniques

Enhancements of Raman Spectroscopy

• Nonlinear Raman spectroscopy. • • •

» » » » »

Resonance-Enhanced Raman Scattering. Surface-Enhanced Raman Scattering. Raman Instrumentation

hyper-Raman effect, stimulated Raman effect, inverse Raman effect, coherent anti-Stokes Raman scattering (CARS), and photoacoustic Raman spectroscopy (PARS)

• Time-Resolved Raman (TR) Spectroscopy • Raman Microscopy • FT-Raman Spectroscopy

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Nonlinear Raman

TR-Raman

1 1 P =αE + βE2 + γE3 +...... 2 6

Transition schemes involved in nonlinear Raman spectroscopy(Joh n R. Ferraro,1994). Simplified diagram of the experimental apparatus for the optically sensitized triplet generation/TR3 studies. FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Microscopy

Thermal Fluid Measurement and Diagnostic MMJ 2413

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FT-Raman

Optical Path for laser input optics and transfer of the Raman signal to the monochromator for microprobe sampling (John R. Ferraro,1994). FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

Optical diagram of a typical FT-Raman experiment. (John R. Ferraro,1994). DR MAZLAN 2006

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Raman application: Species concentration, Particle Size, Temperature

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Figure 4.2: Raman image and intensity profiles of a hydrogen flame, excited with 248 nm excimer laser light. Thermal Fluid Measurement and Diagnostic MMJ 2413

Raman LIF-Turbulent combustion

Experimental setup for the combined Raman/LIF measurements (R. Bombach et. al)

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Spontaneous Raman Scattering • The initial energy of the photon when interacting with the molecule may proceed with unchanged energy (Rayleigh), or have decreased energy (Raman Stokes scattering) or increased energy (Raman antiStokes scattering).

Flame or Plasma

Excited Electronic Level

• Enhancement technique - Resonance enhance Raman scattering, Surface-enhanced Raman Scattering, and Raman Instrumentation consideration.

Virtual Level

• Special techniques - Nonlinear Raman Spectroscopy, FT-Raman Spectroscopy Raman Microscopy Surface-Enhanced Raman Scattering. Resonance-Enhanced Raman Scattering. Time-Resolved Raman (TR) Spectroscopy.

v+1, J v, J

• Application - temperature measurement, species concentration and contaminant identification and particle size distribution had also been discussed FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Beam Dump

Fixed Frequency Laser

• Five major components; Excitation source, sample illumination and scattered light collection system, sample holder, monochromator or spectrograph, and detection system.

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Photomultiplier or CCD Array

Spectrometer

Species-specific, spatially resolved, quantitative, weak signal Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Measurements in Supersonic H2/N2/O2 Flames Cheng, Wehrmeyer, and Pitz, NASA Contractor Report 189544 (1991).

Raman Measurements in Supersonic H2/N2/O2 Flames

Cheng, Wehrmeyer, and Pitz, NASA Contractor Report 189544 (1991).

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Measurements in Supersonic H2/N2/O2 Flames

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Spectrum of Methane

Cheng, Wehrmeyer, and Pitz, NASA Contractor Report 189544 (1991).

D. Stephenson, JQSRT, Vol. 14, 1291 (1974). FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Measurements in Supersonic H2/N2/O2 Flames

Raman Spectrum of Propane

Cheng, Wehrmeyer, and Pitz, NASA Contractor Report 189544 (1991).

D. Stephenson, JQSRT, Vol. 14, 1291 (1974). FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Measurements in High-Pressure H2/N2/O2 Flames

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Measurements in High-Pressure H2/N2/O2 Flames

Kojima and Nguyen, Meas. Sci. Tech., Vol. 15, 565 (2004)

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Thermal Fluid Measurement and Diagnostic MMJ 2413

Kojima and Nguyen, Meas. Sci. Tech., Vol. 15, 565 (2004)

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Polarization Suppression of LIF Interferences Raman Measurements in HighPressure H2/N2/O2 Flames

Kojima and Nguyen, Meas. Sci. Tech., Vol. 15, 565 (2004)

Egermann et al., Appl. Opt., Vol. 43, 5564 (2004) FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Line Imaging

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Line Imaging

Reckers et al., Appl. Opt., Vol. 32, 907 (1993). FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

Reckers et al., Appl. Opt., Vol. 32, 907 (1993). DR MAZLAN 2006

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Line Imaging

Raman Line Imaging

P. C. Miles, Appl. Opt., Vol. 38, 1714 (1999). P. C. Miles, Appl. Opt., Vol. 38, 1714 (1999). FKM UTM

Thermal Fluid Measurement and Diagnostic MMJ 2413

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Miles and Barlow, Meas. Sci. Tech., Vol. 11, 392 (2000).

Miles and Barlow, Meas. Sci. Tech., Vol. 11, 392 (2000). Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Line Imaging

Raman Line Imaging

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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Raman Line Imaging

Raman Line Imaging

Miles and Barlow, Meas. Sci. Tech., Vol. 11, 392 (2000). Miles and Barlow, Meas. Sci. Tech., Vol. 11, 392 (2000). FKM UTM

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Raman Planar Imaging

Sijtsema et al., Opt. Lett., Vol. 24, 664 (1999). FKM UTM

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Thermal Fluid Measurement and Diagnostic MMJ 2413

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