Raman Spectroscopy - University Of California, Irvine

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Raman spectroscopyInformation from Raman SpectroscopycharacteristicRaman frequencieschanges infrequency ofRaman peakparallelperpendicularpolarisation ofRaman peakcomposition ofmateriale.g. MoS2,MoO3stress/strainstatee.g. Si 10 cm-1 shift per% straincrystal symmetry andorientatione.g. orientation of CVDdiamond grainswidth of Ramanpeakquality ofcrystalintensity ofRaman peakamount ofmateriale.g. amount of plasticdeformatione.g. thickness oftransparent coating

Collecting the lightThe coupling of a Raman spectrometer withan optical microscope provides a number ofadvantages:1) Confocal Light collection2) High lateral spatial resolution3) Excellent depth resolution4) Large solid collection angle for theRaman light

The basic function of a Raman system Deliver the laser to the sampling point– With low power loss through the system– Illuminating an area consistent with sampling dimensions– Provide a selection/choice of laser wavelengths Collect the Raman scatter– High aperture– High efficiency optics– High level of rejection of the scattered laser light Disperse the scattered light– Short wavelength excitation requires high dispersion spectrometers Detect the scattered light Graphically / mathematically present the spectral data

Laser wavelength selection concerns for classical RamanAs the laser wavelength gets shorterRaman scattering efficiency increasesThe risk of fluorescence increases (except deep UV)The risk of sample damage / heating increasesThe cost of the spectrometer increases

Raman light sourceSystem basics: lasers1) UV lasersCommon excitation wavelengths2) visible lasers244 nm- biological, catalysts(Resonance Raman)3) NIR lasers325 nm- wide bandgap semiconductors488 nm & 514 nm- semiconductor, catalysts,biological, polymers, minerals & generalpurpose633 nm- corrosion & general purpose785 nm - polymers, biological & generalpurpose830 nm- biological

Generic Raman system flow diagram Illuminate a Sample with an Intense Single Frequency Light Sourcediffractiongratinglasersampledetector Measure the relative frequency shift of the inelastically scattered light

Raman microscopy: Dispersive instrument basicsSystem basics:Grating1) laser2) Rayleigh rejection filter3) grating (resolution)4) CCD Fsamplelaser

Research Grade MicroRaman SpectrometerImage of Si 520 cm-1bandThe Renishaw Raman spectrometer is an imagingspectrographon-axis stigmatic design with a -70 oC Peltier cooledCCD detector. Advanced inverted mode, deep depletionand UV optimized detectors are available as options.We can easily demonstrate the high quality imaging andsystem performance advantages as seen in the imageof the Si 520 cm-1 Raman band on the CCD detector.pixel numberDispersion-640200Intensity14188-2pixel number-12

Delivering the lightPorto notationDelivering the light90 degree scattering x(z,z)y and90 and 180 degree scattering180 degree scattering x(z,z)x’excitation direction (excitation polarization,scattered polarization) scattering directionyxx’The actual excitation and collection directions are the range of angles0 to x1000.9128.3

Delivering the lightDelivering the light (180 degree backscattering)Raman 90% efficient21Holographic notchor edge filterexcitationRaman microscope systems typicallyoperate in with the excitation direction andcollected Raman scattering directionseparated 1800. This mode of collectionand excitation is referred to as “backscattering”.Typically back-scattered Raman collectionnecessitate special optics that operateboth as a Rayleigh filter and as a lasermirror. Holographic notch filters andspecial dielectric mirrors are often theoptics of choice, since they minimize laserintensity loss and Raman scattering lossesthat would otherwise occur when utilizing apartial reflector.Relative laser excitation efficiency andRaman transmission efficiencies can be

Delivering the lightLaser focused spot sizeThe minimum laser focus isdetermined by:1. the focusing optic N.A.2. laser wavefront (distortionor M2)3. How the back aperture ofthe objective is filledRaman spectroscopy utilizing a microscopefor laser excitation and Raman lightcollection offers that highest Raman lightcollection efficiencies.When properly designed, Ramanmicroscopes allow Raman spectroscopywith very high lateral spatial resolution,minimal depth of field and the highestpossible laser energy density for a givenlaser power.It is important to note that the laserminimum focused spot size is not typicallythe same size as the coupled Ramanscattered spot size.The minimum laser focused spot size isoften compromised by improperly matchingthe laser size to the back aperture of anobjective and by wavefront errors inherentto the laser and introduced by the laser

Delivering the lightLaser focused spot sizeWithout consideration of the laser mode quality and wavefront, orsource size the minimum laser focused spot for any optic isdescribed by equation 1:dl 1.22 * λN . A.Minimum laser focus1) Excitation wavelength: λ2) effective numerical aperture : .367854.151.991.250.660.553) dl is determined by twice the Rayleigh criteria of the adjacent distancerequired to spatially resolve the presence of an identical size spots

Delivering the lightLaser focused spot sizeobjective N.A.:0.75Excitation wavelength/nm:514.5Airy disk pattern1.2Separation distance0.44 um1Relative IntensityThe laser focused spotsize does not necessarilydefine the lateral spatialresolution of the Ramansystem. The lateralspatial resolution, is oftendiscussed in terms of theRayleigh criteria for thecollected Raman light.The Rayleigh criteriarequires that the distancebetween two pointssources of light of equalintensity be greater thanthe distance from thepeak to the first airy diskminimum. Completediscrimination of twoadjacent materials occursat twice the ce/microns1.52.5

The relative energydensity and peakpower for the X5,X20 and X50objectives areshown relative tothe X50 objective.The peak energydensity decreases by 50% for the X20and 87% for the X5objectiveDiffration limited focusx50 (0.75)x20 (0.40)x5 (0.10)1.2relative energy densityIt’s important toremember that theobjective used todeliver the laser lightaffects the laserenergy nsAiry disk calculation for X5, X20 and X50 objective calculated for 514.5 nm l234

Delivering the lightLaser focus and depth of fieldThe system laser focus depth (hl) is determined by:1) Excitation wavelength: λ2) Microscope objective focal length : f3) Effective laser beam diameter at the the objective backaperture: Dl fhl 2.53 * λ Dl 2DO NOT CONFUSE LASER FOCUS DEPTH WITH CONFOCAL COLLECTION DEPTH

Delivering the lightLaser focus and illuminated volumeThe system laser focus volume (τl) is determined by:1) Excitation wavelength: λ2) Microscope objective focal length : f3) Effective laser beam diameter at the the objective backaperture: Dl fτ l 3.21* λ Dl3 4DO NOT CONFUSE LASER FOCUS VOLUME WITH CONFOCAL COLLECTION VOLUME

Collecting the lightσ 4/π *(N.A.)2Opaque sampleN.A. vs. IntensityMeasured vs. calculatedObjective5x10X20X50Xulwd50X100X100X oilN.A0. σ0. immersion objectiveincrease is likely due toreduced reflection lossesSi Raman intensity2.521.510.500Solid collection angle is proportional to (N.A.)2 not 1/(f/#) 20.51numerical aperture1.5

Collecting the lightRelative collection volumeThe system laser focus volume (τl)6Macro-sampling isimproved with longerwavelength excitationRelative volume543 fτ l 3.21* λ Dl 43210400500600700Wavelength (nm)800900

Extended scanning(Renishaw patent EP 0638788)From the Renishaw Raman software the user can select: a fixed grating measurement with a spectrum 'window'of 400 cm-1 to 1000 cm-1 (configuration dependent) a unique 'extended scanning' facility allowing the userto choose any Raman shift range up to about 10000 cm-1(configuration dependent). Essential for extended rangescanning for Raman and photoluminescenceExtended scanning is implemented by moving the grating andthe charge generated on the CCD camera synchronously.This feature is NOT available on any other instrument and isKEY to system performance

CCD Basics

Extended scanning: how it works

Extended scanning vs stitched scanningAdvantages of extended scanninguse a single gratingno stitching required and no “discontinuities” at joinsflexible wavenumber coverage (up to 10000 cm-1 )pixel-to-pixel variation is averaged out - enhancing noise reductionno compromise on resolution across the scanned rangesimple to use

To acquire useful Raman spectra all you need is:Sufficient spectral and spatial resolution and coverageThe ability to separate spectral peaks narrower than the narrowestanticipated spectral features of your sampleThe ability to collect all of the spectral data required for the analysisThe ability to optically restrict the data collection to an area / volumesmall enough to eliminate acquisition of unwanted spectral data ofnearby substancesAdequate S/NThe ability to collect and detect enough photons to distinguish theirelectronic signal above system generated noise before the sample changesor dies.RepeatabilityThe ability to consistently get the same right or wrong values

Confocal Raman collectionConfocal Raman microscopy without pinhole opticsgratingSlitSlitConjugate image planes - Square pinholeCCDCCDSlitCollectionopticPreslitfocusing lensCCDThe use of a stigmatic spectrograph and stigmatic microscope-spectrometercoupling optics creates two additional conjugate image planes at the slit andCCD eliminating the need for pinhole optics!Spatial filtering

Confocal Raman collection2 um polymer filmαβχδηSipolymerSilicon WaferCounts1000500 50XHigher numericalaperture objectiveseffectively eliminate theRaman spectrum ofunderlying layers!100X0100X oil400600800100012001400Raman Shift (cm-1)160018003: CONFO 15Confocal 100XLaser: 15802.78cm-1White Light Correction:2000

Spectral resolution and coverage are controlled by focal length and groove density

Spectrometer issues associated with different excitationsShorter wavelength excitation requires higher dispersion spectrometers andproduce higher levels of stray light in the system.1 nm is equivalent to:160 cm-1 @ 250 nm excitation94 cm-1 @ 325 nm excitation38 cm-1 @ 514 nm excitation16 cm-1 @ 785 nm excitation

System parameters that affect spectral resolution and coverage The dispersion of the spectrometer– Focal length– Grating groove density Multiple gratings for resolution/coverage trade-off For using multiple excitation wavelength– Grating rotation– Optical aberrations in the spectrometer– Mutichannel Detector Pixel size Width (under certain circumstances)– Laser Wavelength stability Wavelength choice

Raman microscopy: spectral resolutionSpectrometer resolutionThe slit-width determined resolution of the spectrometer isdetermined by the convolution of the entrance slit with theCCD pixel.ccdSpectral linesspectrum

Raman microscopy: spectral resolutionSpectrometer resolution is best determined by measuring the air spectrum40000The air spectrum shows thatsystem resolution is limited to35000 0.7 cm-1 FWHM utilizing 633 nmexcitation.Counts30000O2 & N225000200001500010000

When the spectrometer determines measured spectral linewidthsIncreasing the entrance slit increases light throughput but decreases resolutionRaman spectrum of air30 min, 7 mW, 633 nm.200000Resolution 3.4 cm-1vs.Resolution 0.70 cm-1Counts150000100000100 um30 um15 um50000

Trading spectral resolution for throughputCountsIncreasing the entrance slit increases throughput but decreases resolution4000002400 l/mm gratingRaman spectrum ofCCl4, 10 - 1 secaccumulations withdifferent slit setting300000Intensity increases 7fold, resolutiondecreases 5 fold200000100 um30 um15 um100000

Sample determines measured spectral linewidthsSingle static scan with 600 l/mm, 10 stitched static scans with 2400 l/mThe caffeine Ramanspectrumidentical laser powers1.41.2Counts110 secResolution 7 cm-1(600 l/mm). 2 minResolution 3.5 cm-1(2400 l/mm)

Sample determines measured spectral linewidthsMatching the spectrometer resolution and the and CCD pixel resolution to the natural linewidthsof the sample optimizes S/N.7 600 l/mm gratingDecreases measurement time.6 an order of magnitude,Increases S/N an order of.5 magnitude.Counts. resolution isdetermined by the sample

System parameters that affect S/N Laser– Power– Wavelength– Modality– Stability– Delivery optics Collection Optics– Aperture– Focus Diffraction limited spot size– Transmission– Robustness

Factors affecting S/N

Select a CCD for best Raman performanceWhat limits the CCD performance?1. Read noise: How many photon generated electrons are required to achievea signal level greater than the read noise?Raman systems that require off chip binning increase read noise to thesquare root of the number of pixels binned.2. Dark Charge rate: How long can you integrate before the binned CCDpixels generate a charge equivalent to the read noise?At the integration time that the dark charge signal contributes to the noiseeither through shot noise or uniformity of response, it must be subtracted.3. Uniformity of response: How many photon generated electrons can bemeasured before the shot noise is exceeded by the non-uniformity ofresponse?At the point uniformity of response noise exceeds shot noise the pixels mustbe read out individually (without binning) for response correction.

Optimal CCD operating temperatureThe best CCD temperature operation is determined by the CCD darkcharge rate and the requirements for operation near the detectorlimit of 1050 nm Low temperatures decrease the CCD dark charge rate. The CCD darkcharge rate decreases 50% for each 6-9 degree decrease in operatingtemperature.Dark Charge e/p/sQd 122 * T 3 * eQd 0-6400TQd dark charge rate (e/p/s) atoperating temperature TQdo - dark charge rate at referencetemperature (typically 23-25 oC)A1A-CCD02-06 Deep Depletion Sensor Issue 3, January2000Dark Charge rate e/p/s1010.10.010.001-80-60-40Temperature C-200

Select a CCD for best Raman performanceSelect response uniformity rather than QERenishaw CCDtypicalresponsecurve. Thepeak QE is 50%, butthe responseuniformity isan order ofmagnitudebetter thanwith higher QECCD chips

StreamLine StreamLine technology– Unique Renishaw technology(patent pending)– Combination ofhardware and software– Enables very fastRaman imaging of samples Application areas––––––PharmaceuticalsMaterials scienceSemiconductorsPolymersBiosciencesetc.

Spectral imaging Acquire data from different pointson the sample. Generate maps based onparameters of resulting spectra.Examples:– Univariate: intensity of band– Multivariate: chemometrics: Component analysis based onreference samples Principal component analysis (noreferences)

Mapping stage repeatability Measure the Raman spectrum of 1 µm Siparticle with 1 µm laser spot (backlash of 10 µmenabled) Move away from then return to the particle torepeat the Raman measurement (32 times eachdirection) Compare performance of the motorized mappingstage with the 0.1 µm encoders on to theperformance with the encoders offSpecification:unencoded2 µmencoded0.3 µm

The Si particle

Raman line mapping Method– Generate laser line on sample– Simultaneously acquire spectrafrom positions along the line– Move line over sample,perpendicular to its length Advantages– Larger area illuminated by line Disadvantages– Stop/start movement overhead– Artefacts line uniformity

StreamLine Move line the other way! Synchronise the stage and thedetector Advantages– Smooth fast continuous movement– Artefacts eliminated– Large area illuminated by line

Features of StreamLine imaging StreamLine offers:– Power density up to 100x less than point laser configurations– No joining or uniformity artefacts– Macro (whole tablet) and micro ( 1 µm) sampling capabilities– Zero dead time between sequential spectral acquisitions– Confocal information maintained– High spectral resolution options available– Multi-wavelength capabilities from the UV to NIR– High speed with unparalleled data quality

StreamLine Technology for very fast Ramanimaging Unique Renishaw technology(patent pending) Innovative hardware, uniquesoftware Collect excellent quality data wherepoint by point would damagesample Parallel data readout, synchronisedwith sample movement100µm

StreamLine imaging: how it works?– Each sample point passes beneath each part of the laser line– The charge is stepped synchronously with the stage movement– Parallel data readout

White-light montage Used for detailed sample survey 4 4 white-light montagegenerated with 50 objective Montage can then be used todefine multiple imagingexperiments Multiple experiments may bequeued White-light image saved withspectral data

StreamLine in action Example StreamLine video Silicon target with metallisedstructure, imaged with 532nm laser 4 x 4 montage white-light imageused to define experimental area Imaged area bigger than 50xobjective field of view Live imaging of Si 520cm-1 band Bicubic interpolation applied toimage during acquisition

Metallised Si target analysis Line profile along the Y axis Feature size approximately 5 µm

Image quality comparisonImage quality comparisonStreamLine 1 minute, 40 secondsPoint by point 1hour, 6 minutes Same area on tablet analysed using point by point and StreamLine techniques Image generated using direct classical least square (DCLS) multivariate method Image shows distribution of Aspirin, Paracetamol and Caffeine components Identical data quality

Image of complete tooth section First ever whole tooth Raman image Different regions clearly indentified Color coding:– Yellow: enamel– Green: dentine– Red: fluorescent areas Details– 9 mm x 16 mm area– 84,024 spectra– 20 minutes– 785 nm excitation

Spectrum from dentine region of tooth

Dental caries polarisation images Image is a ratio of two data sets:– Parallel-polarisation– Crossed-polarisation Color coding:– Red: strong polarisation dependence Sound enamel– Green: weak polarisation dependence Carious region Details––––1.5 mm x 3.4 mm area42,642 spectra27 minutes785 nm excitation StreamLine is compatible with the fullrange of spectral options available forthe inVia Raman microscope

Dental caries curve-fit analysis image Curve fit data analysis onP-O symmetric stretchband– Peak width– Peak position Details––––1.5 mm x 3.4 mm area42,642 spectra27 minutes785 nm excitation

Whole ink character imagingFirst ever whole ink character Raman image 43,400 spectra 29 minutes 514 nm 20x objective 30 µm spatial resolution Image created usingcomponent methodRaman ink imageWhite light montage

Whole ink character imagingHigh quality ink spectrum from image (noise filtered)

Whole ink character imagingImage can also reveal pen contact on paperBlue – paperRed – paper with pen contactaway from inkUseful information provided onpen angle during stroke

Crossed ink example 1: dual crossed ink linesFirst ever Raman crossed lineimageDouble crossed line exampleusing two black ball point pensImage collected of all lines and paper inone experiment Details–––––1040 µm (X) by 2607 µm (Y)90,440 spectra90 minutes total time514 nm excitation20x objective

Crossed ink example 1: dual crossed ink linesComponent Raman image ofink 1 (green)Shows smearing of top horizontal lineAlso the image provides information onthe direction of the crossingThis suggests that the top ink 1 line isbeneath a further line crossing it.Directionofsmearing

Crossed ink example 1: dual crossed ink linesComponent Raman image overlayfrom WiRE 3 – confirms order ofdepositionTop cross – Ink 1 (green) under ink 2Bottom cross – Ink 2 (red) under ink 1Ink 1 (green)Ink 2 (red)Paper (blue)

Crossed ink example 2: single crossed ink linesSingle crossed line example using two black ball point pens Details–––––990 µm (X) by 1430 µm (Y)47,422 spectra33 minutes total time514 nm laser wavelength20x objective

Crossed ink example 2: single crossed ink linesComponent Raman imageoverlay from WiRE 3superimposed on white lightimageCross – Black ink 1 (green) over blackink 2 (red)Black ink 1 (green)Black ink 2 (red)

Crossed ink example 2: spectra from imageBlack ink 2 (red)Black ink 1 (green)

Raman and PL imaging of polycrystalline CVD diamond film CVD diamond sample grownonto silicon substrate usingchemical vapour deposition(CVD) method Rough growth surface issubsequently polishedoptically flat Raman andphotoluminescencemeasured in sequentialexperiments Curve-fit analysis used forimage generation 18,000 spectra collected in 6minutesDiamond peak position

Raman and PL imaging of polycrystalline CVD diamond filmDetails of spectral analysisPhotoluminescence rangeRaman range1.68 eV [Si-V]0(intensity capped)1332 cm-1Diamond1.77 eV1.95 eV[N-V]- Standard spectralresolutionconfiguration usedfor Raman bands,lower resolutionused forphotoluminescencefeatures

Raman and PL imaging of polycrystalline CVD diamond film 50,000 spectra collected in 15 minutes with 0.5 micrometer resolution Sequence derived from 2 imaging experiments (Raman and Photoluminescence) A and B highlight two areas of highly twinned crystal facets exhibiting five-foldsymmetry-1 Raman-1 Raman-10 mRamanbandIntensityof1.68eV[Si-V]bandAB

Diamond nucleation region Diamond film– nucleation side of a free-standingdiamond film Map shows:– Top image: Diamond-rich area 1332cm-1 diamond band component– Bottom image: Graphitic-rich region G and D bands graphite components Details– 110 µm 110 µm area– 10,000 spectra– 10 minutes

Si-Ge cross hatch Semiconductor sample– SiGe layer deposited onto substrate– Graded layer with increasinggermanium content towards layersurface– Crosshatch structure is notengineered– Pattern is generated a mechanismfor strain relief Map shows:– Variation in Si-Si 510 cm-1 bandposition ( 0.2 cm-1 positional bandshift) Details––––55,000 spectra13 minutes0.5 micrometer resolution532 nm excitation

Carbon nanotube lattice structuresMWTSWNT Raman spectrum

Resonance RamanIf the wavelength of the laser is close to an excited electronicstate of a bond in molecule, i.e. where it is strongly absorbed orfluoresces, the signal enhancement can be increased by a factorbetween 100 and 10,000.Advantage: You can select a wavelength to enhance the sensitivity toa particular type of bond or vibrations.Potential disadvantages:increased fluorescenceincrease absorption/heatingIn the study of carbon nanotubes multiple laserwavelengths are used to increase sensitivity tospecific vibrational modes within a molecule.

Resonance Raman spectroscopy of SWNTSince the Raman spectral measurment for nano-tubes is typically a resonance Raman measurementthe excitation wavelength can dramatically affect the spectral feature intensity and shift.C-CRBM1Counts.8785 nm244 nm.6.4.20 nm and 780 nm excited Raman spectra of nanotubes244

Resonance Raman of SWINTs

Raman spectroscopy of 2500Raman shift / cm-1514 nm excited and 488 nm excited Raman spectra MWNT material30003500

Raman and FraudLewis, I. R.; Edwards, H. G. M., Handbook of Raman Spectroscopy: From the Research Laboratory to the

vory or Plastic?Lewis, I. R.; Edwards, H. G. M., Handbook of Raman Spectroscopy: From the Research

The Vinland Map: Genuine or Forged?Brown, K. L.; Clark, J. H. R., Anal. Chem. 2002, 74,3658.

The Vinland Map: Forged!Brown, K. L.; Clark, J. H. R., Anal. Chem. 2002, 74,3658.

Surface-Enhanced Raman Scattering (SERS)SERS: Surface Enhanced Raman ScatteringDiscovered in 1977, Jeanmire et al. & Albrecht et al.--Strongly increased Raman signals from molecules attachedto metal nanostructures--SERS active substrates: metallic structures with sizeabout 10--100 nm (e.g. colloidal Ag, Au, roughened surfaces)General contributions:1)Electromagnetic field enhancement2) Chemical ‘first layer’ effectHaynes, McFarland, and Van Duyne, Anal. Chem.,77, 338A-346A (2005).

SERS Enhancement MechanismsChemical Mechanism:Laser excites (a) new electronic states arising fromchemisorption or (b) shifted or broadened adsorbateelectronic states yielding a resonance condition. Short range (1-5 Å) No roughness requirement Contributes EF 102 – 104Electromagnetic Mechanism:LSPR induces large electromagnetic fields at roughenedmetal surface where molecules are adsorbed. Long range (2-4 nm) Affected by all factors determining LSPR Contributes EF 104

Localized Surface Plasmon ResonanceThe resonance results in (1) wavelength-selective extinction and (2) enhanced EMfields at the surface.Spectral location of the LSPR is dependent upon particle size, shape, composition,and dielectric environment.

Localized Surface Plasmon ResonanceNon-resonantResonant1) Resonant λ is absorbed2) EM fields localized at nanoparticle surface

Nanostructured ancham-a/0000/77/i17/pdf/905feature vanduyne.pdf

Commercial SERS SubstratesD3 produces the Klarite range of substrates for SurfaceEnhanced Raman Spectroscopy. Klarite substrates enable faster,higher accuracy detection of biological and chemical samples atlower detection limits for a wide range of applications inhomeland security, forensics, medical diagnostics andpharmaceutical drug discovery. Manufactured using techniquesfrom semiconductor processing Klarite substrates offer highlevels of enhancement and reliability.

ReferencesRaman Microscopy: Developments and Applications,Applications, G. Turrell,Turrell, J. Corset, eds.eds. (Elsevier Academic Press,1996)Introductory Raman Spectroscopy,Nakamoto, C.W. Brown, Academic Press, 2003.Spectroscopy, J.R. Ferraro, K. Nakamoto,Raman Spectroscopy for Chemical Analysis,Interscience, 2000).Analysis, R.L. McCreery (Wiley Interscience,Handbook of Raman Spectroscopy,eds. (Marcel Dekker,Dekker, 2001)Spectroscopy, I.R. Lewis, H.G.M. Edwards, eds.Raman Technology for Today’Spectroscopists, 2004 Technology primer, Supplement to SpectroscopyToday’s Spectroscopists,magazine.FT Raman spectroscopy, P. Hendra et al., Ellis Horwood.Raman and IR spectroscopy in biology and chemistry, J. Twardowski and P. Anzenbacher, Ellis Horwood.Ch 18 in Skoog, Holler, Nieman, Principles of Instrumental Analysis, Saunders.

Raman Websites and On-Line da?chId 6&type Education(many links including,An Introduction to Raman Spectroscopy: Introduction and Basic Principles, by J. Javier let.com/http://www.jobinyvon.com

Raman spectroscopy utilizing a microscope for laser excitation and Raman light collection offers that highest Raman light collection efficiencies. When properly designed, Raman microscopes allow Raman spectroscopy with very high lateral spatial resolution, minimal depth of field and the highest possible laser energy density for a given laser power.

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