Molecular spectroscopy is the analysis of molecular species by measuring the interaction of light with a specific sample. The absorption, emission, and/or reflection from a sample of light with wavelengths in the ultraviolet, visible, and/or infrared regions is characteristic of the various molecular vibrations, rotations, and other changes in the energy states of the interacting chemical species, and are unique to different molecular species. Molecular spectroscopy techniques are generally nondestructive and broadly applicable. Ultraviolet/visible (UV/Vis), near-infrared (NIR), and infrared (IR) spectroscopy techniques typically measure the sample’s absorption of the particular portion of the light spectrum they probe. Fluorescence spectroscopy irradiates a sample, but instead of measuring the absorbed energy, it measures the wavelengths and power of the energy that is re-emitted from the sample due to the initial excitation irradiation. Raman spectroscopy measures the spectrum of light scattered from the molecules in a sample. Nuclear MR investigates the absorption of radiofrequency electromagnetic radiation due to interactions with the magnetic properties of the nuclei in the sample. Refractometry, ellipsometry, and color measurement investigate other ways in which samples interact with light.
December 11, 2018