Fourier transform Raman mapping

Fourier-Transform Infrared (FTIR) spectroscopy as well as Raman spectroscopy are well established as methods for structural analysis of compounds in solution or when adsorbed to surfaces or in any other state. Analysis of the spectra provides information of qualitative as well as of quantitative nature. Very recent developments, FTIR imaging spectroscopy as well as Raman mapping spectroscopy, provide important information leading to the development of novel materials. If applied under optical near-field conditions, these new technologies combine lateral resolution down to the size of nanoparticles with the high chemical selectivity of a FTIR or Raman spectrum. These techniques now help us obtain information on molecular order and molecular orientation and conformation [1],... 

An alternate approach is to perform coherent Raman spectroscopy in the time domain rather than in the frequency domain. In this case, a single laser that produces short pulses with sufficient bandwidth to excite all of the Raman modes of interest is employed. One pulse or one pair of time-coincident pulses is used to initiate coherent motion of the intermolecular modes. The time dependence of this coherence is then monitored by another laser pulse, whose timing can be varied to map out the Raman free-induction decay (FID). It should be stressed at this point that the information contained in the Raman FID is identical to that in a low-frequency Raman spectrum and that the two types of data can be interconverted by a straightforward Fourier-transform procedure (12-14). Thus, whether a frequency-domain or a time-domain coherent Raman technique should be employed to study a particular system depends only on practical experimental considerations. 

For Raman microscopy, the most common spectrometer system consists of a visible laser coupled to a polychromator and a CCD detector, although near-infrared Fourier transform spectrometers cffe also used. The CCD detector can be used in a variation of Raman microscopy known as Raman imaging a special optical filter allows only one Stokes fine to reach the two-dimensional detector, which then contains a map of the distribution of the intensity of that line in the illuminated area. 

Unger M, Sato H, Ozaki Y, Fischer D, Siesler HW. Temperature-dependent Fourier transform infrared spectroscopy and Raman mapping spectroscopy of phase-separation in a poly(3-hydroxybutyrate)-poly(L-lactic acid) blend. Appl Spectrosc 2013 67 141-148. 

Physical and chemical characterization methods are essential to assess aspects such as material and processing quality. Raman microprobe is an analytical tool coupled to an optical microscope. Elemental analysis using the x-rays emitted from the specimens in the electronic microscopy techniques can be used for local composition determination or to obtain a map of the distribution of a certain element in a wider area wavelength and energy-dispersive x-ray spectrometers are used for these purposes. Fourier transform infrared spectrometer is widely used for the qualitative and quantitative analysis of adhesives, the identification of unknown chemical compounds, and the characterization of chemical reactions. Thermal methods such as thermomechanical analysis and differential scanning calorimetry are discussed as valuable tools for obtaining information during postfracture analysis of adhesively bonded joints. 

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