Free induction decay definition

Free fatty acid (FFA) analysis definition of FFA, 471 lipid composition, 471 -472, 476-477 Free induction decay (FID), 22 (fig.), 23 Free radicals lipid oxidation, 535-536 lipids, 525... 

Fig. 2.—Proton, Free-induction Decay Signal45 of a Solution of 6-Deoxy-1,2 3,4-di-O-isopropylidene-6-phthalimido-o-D-galactopyranose (54) (0.06 mg) in 4 1 (v/v) Chloro-form-d (Commercial, 100% )-Hexafluorobenzene (0.06 ml) Contained in a Microcell. [The f.i.d. signal was acquired in 419 sec by using the crossed-coil mode with hetero-nuclear, internal, field-frequency stabilization on fluorine-19, with 1,024 pulses at 90 MHz, tp 40 jusec, St 400 /jsec, and 1,024 datum points (for definitions, see text).]...

Within the density-matrix formalism (Vol. 1, Sect. 2.9) the coherent techniques measure the off-diagonal elements pab of the density matrix, called the coherences, while incoherent spectroscopy only yields information about the diagonal elements, representing the time-dependent population densities. The off-diagonal elements describe the atomic dipoles induced by the radiation field, which oscillate at the field frequency radiation sources with the field amplitude Ak(r, t). Under coherent excitation the dipoles oscillate with definite phase relations, and the phase-sensitive superposition of the radiation amplitudes Ak results in measurable interference phenomena (quantum beats, photon echoes, free induction decay, etc.). 

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