Spatially resolved chemical information

FT-IR and Raman spectroscopic imaging techniques may employ three general approaches to obtain spatially resolved chemical information mapping, imaging with a multi-element detector, and spatial encoding and decoding. 

The ESRI experiments described in our publications and summarized in this chapter led to spatially resolved information on the effect of treatment conditions, amount of stabilizer, and polymer composition on the degradation rate. In the heterophasic systems studied in our laboratory, ESRI has identified specific morphological domains where chemical processes are accelerated. The combination of ID and 2D spectral-spatial ESRI experiments led to mapping of the stabilizer consumption on two length scales within the sample depth on the scale of a few mm, and within morphological domains on the scale of a few gm. 

In comparison with other measurement methods, NMR has important strengths. Its great virtue is its noninvasive nature, allowing one to obtain spatially resolved metabolic profiles and to investigate metabolomics in vivo. 10 There is little or no sample preparation. It is nondestructive. It is information-rich with regard to the determination of molecular structures because it can detect different chemical groups of metabolites simultaneously. 

Beyond imaging, CARS microscopy offers the possibility for spatially resolved vibrational spectroscopy [16], providing a wealth of chemical and physical structure information of molecular specimens inside a sub-femtoliter probe volume. As such, multiplex CARS microspectroscopy allows the chemical identification of molecules on the basis of their characteristic Raman spectra and the extraction of their physical properties, e.g., their thermodynamic state. In the time domain, time-resolved CARS microscopy allows recording of ultrafast Raman free induction decays (RFIDs). CARS correlation spectroscopy can probe three-dimensional diffusion dynamics with chemical selectivity. We next discuss the basic principles and exemplifying applications of the different CARS microspectroscopies. 

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