Description

Raman spectroscopy is a non-destructive technique based on the inelastic scattering of light (Raman scattering) that allows for microscopic examination of minerals and other materials. Excited by monochromatic light (laser), the specimen emits scattered light with a different wavelength than the laser light. The difference in the wavelength (Raman-shift) contains vibrational information of molecules in the specimen, and by that of its composition and structure.

Instrumentation

HORIBA Jobin Yvon LabRAM HR 800, equipped with:

Multiple laser sources:

• air-cooled Nd:YAG laser (λ = 532 nm)
• air-cooled HeNe laser (λ = 633 nm)
• diode laser (λ = 785 nm)

Spectrograph:

• 800 mm focus length
• covers the spectral region 450–1100 nm
• spectral resolution 1–2 cm^-1 (in high resolution mode)

Detector:

• Peltier cooled multichannel CCD detector (1024 pixel)
• covers the spectral region 400–1050 nm
• laser specific notch filter assemblies eliminate the laser line in the Raman spectrum

Integrated confocal microscope:

• an Olympus BX41with white light illumination for observation in transmitted and reflected mode
• 0.1 µm high precision motorised XY translation stage for Raman confocal mapping
• resolution of confocal spot analysis: lateral <2 µm, axial <4 µm

Software

LabSpec:

• Spectrometer program controls instrument functions and data acquisition
• Control of the external components (TV camera, motorised XY stage)
• Spectral data treatment (baseline correction, spectral subtraction, band fitting, de-convolution, …)

Other software:

• Peakfit, allows detailed analysis of spectral data
• Spec ID, a spectral library for identification of minerals

References

Wiederkehr M., Bousquet R., Ziemann M. A, Berger A. & Schmid S. M., 2011, 3-D assessment of peak-metamorphic conditions by Raman spectroscopy of carbonaceous material: an example from the margin of the Lepontine dome (Swiss Central Alps), International Journal of Earth Sciences, accepted

Nasdala, L., Smith, D. C., Kaindl, R., and Ziemann, M. A., 2004. Raman spectroscopy: Analytical perspectives in mineralogical research. - In: Beran, A., and Libowtzky, E.: Spectroscopic methods in Mineralogy; EMU - Notes in Mineralogy, Vol. 6, 281 - 343. (Budapest, Eötvös University Press)

Schrader, B. (Ed.), 1995. Infrared and Raman spectroscopy: methods and applications. VCH Verlagsgesellschaft Weinheim u.a.

Hawthorne, F. C. (Ed.), 1988. Spectroscopic methods in Mineralogy and Geology. Reviews in Mineralogy, Vol. 18.