Nuclear magnetic resonance spectroscopy electromagnetic radiation, absorption

Abscicic acid, 1027 Absolute configuration, 267—271, 292 Absorption of electromagnetic radiation, 489 in infrared spectroscopy, 518 in nuclear magnetic resonance spectroscopy, 490—493 in ultraviolet-visible spectroscopy, 524—525 Absorptivity. See Molar absorptivity Acetaldehyde, 655 bond angles, 657 enolization of, 706... 

The techniques available to achieve molecular structure determinations are limited. They include structural analysis with diffraction techniques—such as electron, neutron, and x-ray diffraction—and various absorption and emission techniques of electromagnetic radiation—such as microwave spectroscopy and nuclear magnetic resonance (NMR). For molecules with unpaired spins a companion technique of electron spin resonance spectroscopy (ESR) is highly informative. 

Spectroscopy produces spectra which arise as a result of interaction of electromagnetic radiation with matter. The type of interaction (electronic or nuclear transition, molecular vibration or electron loss) depends upon the wavelength of the radiation (Tab. 7.1). The most widely applied techniques are infrared (IR), Mossbauer, ultraviolet-visible (UV-Vis), and in recent years, various forms ofX-ray absorption fine structure (XAFS) spectroscopy which probe the local structure of the elements. Less widely used techniques are Raman spectroscopy. X-ray photoelectron spectroscopy (XPS), secondary ion imaging mass spectroscopy (SIMS), Auger electron spectroscopy (AES), electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spectroscopy. 

Nuclear magnetic resonance (NMR) spectroscopy is based on the measurement of absorption of electromagnetic radiation in the radio-frequency region of roi hly 4 to 900 MHz. In contrast to Uy, visible, andlR absorption, nuclei of atoms rather than outer electrons are involved in the absorption process. Furthermore, to cause nuclei to develop the energy states required for absorption to occur, it is necessary to place the analyte in an intense magnetic field. In this chapter we describe the theory, instrumentation, and applications cfhiMR spectroscopy. 

Nuclear magnetic resonance (NMR) spectroscopy is based on the absorption of radiofrequency electromagnetic radiation (of the order of 100 MHz) by atomic nuclei [mainl> protons proton magnetic resonance (PMR), but also C, N, F, Na, Mg, etc.] in substances placed ir... 

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