Raman Spectroscopy Flashcards
Portable Raman spec can be used in situ to analyse….
Wall murals that cannot be moved.
Four advantages of Raman spec….
Can be portable.
Non destructive.
No sample prep is required.
Can analyse small samples.
Can be used for art to…
Identify pigments in paintings.
Similar colour pigments can have….
A very different Raman spectra
Can be used with a microscope, Raman microscopy. Three advantages of this are….
Analyse smaller samples.
Higher spatial resolution.
Individual particulates can be targeted for analysis.
Can analyse extraterrestrial samples to determine their….
Chemical composition.
How does it work?
Uses a low energy beam of monochromatic, polarised light to excite sample surface with a high spatial resolution. The light is scattered by the sample, detected and the spectrum is recorded.
The three types of peaks on a Raman spectra….
Peak at zero - Rayleigh scattering, no freq shift occurs.
Peaks at left - Stoke lines, lower freq, more intense.
Peaks at right - Anti-Stokes, higher freq, less intense. Represent energy transferred back to photon.
The shift in frequency corresponds to a change in vibrational energy of the molecule.
Raman scattering is inelastic scattering (no loss of energy). When bombarded with light a small amount of radiation is….
Scattered with a shift in frequency.
Raman spec (and IR) are used to study….
Molecular vibrations. Can determine presence of particular molecule or mineral in a sample. Can determine composition of a sample.
Scattered radiation changes in….
Frequency and wavelength.
Rayleigh scattering - elastic scattering, no energy is ….
Absorbed of emitted.
Some scattered light undergoes a change in frequency (inelastic scattering) and this produces….
Raman spectra.
Energy can be absorbed (Stokes) or emitted…..
Anti-stokes.
Stokes - energy absorbed, more energy goes in than…
Comes out.
