Vibrational Spectroscopic Imaging

Abstract

Vibrational spectroscopy, which probes vibrations within and between molecules, may be divided into four classes: mid-infrared (MIR, also referred to as just infrared (IR)), near-infrared (NIR), terahertz/far-infrared (FIR), and Raman. These techniques, described in earlier chapters, have several features in common: they are rapid, non-destructive, and label-free and can yield information-rich data about both the chemical and physical (e.g. solid state form) properties of samples. NIR, IR and terahertz spectroscopies probe the absorption of infrared light of increasing wavelength (from NIR to terahertz regions). In contrast, Raman spectroscopy is based on a scattering phenomenon and may be used to probe vibrations that occur in both the MIR and terahertz regions. These techniques have become widespread for drug and dosage form characterisation during, for example, synthesis and pharmaceutical processing.