Hyperfine field coupling constant

The remainder of equation (38) describes the multiplet effect, and it can be seen that whether an individual line in the multiplet corresponds to emission or absor ption depends on the signs of the hyperfine coupling constants but is independent of Hq. The nature of the hyperfine field is such that the integral over the whole multiplet is zero if Ag = 0. 

Because of the different properties of the nuclear ground and excited states, the hyperfine coupling constants (A-values) for Mossbauer nuclei are often quoted in units of the internal field, where /I represents an energy and is the... 

Conversion of magnetic hyperfine coupling constants A into internal fields for Fe When the nuclear spin is decoupled from the electronic spin by application of an external field, the hyperfine coupling, according to (4.76), is defined as... 

The electron spin resonance of the nitroxalkylcorrinoids can be readily observed in aqueous solution at room temperature. Both the cobalamin and cobinamide show nitrogen hyperfine coupling constants of 17.2 gauss. A typical spectrum is shown in Fig. 20. The line widths for the low, intermediate, and high field peaks are 1.87, 1.87, and 2.20... 

Spectra of radicals in a dilute single crystal are obtained for various orientations, usually with the field perpendicular to one of the crystal axes. Each spectrum usually can be analyzed as if they were isotropic to obtain an effective g-value and hyperfine coupling constants for that orientation. Since the g- and hyperfine-matrix principal axes are not necessarily the same as the crystal axes, the matrices, written in the crystal axis system, usually will have off-diagonal elements. Thus, for example, if spectra are obtained for various orientations in the crystal vy-plane, the effective g-value is ... 

Here, /3 and / are constants known as the Bohr magneton and nuclear magneton, respectively g and gn are the electron and nuclear g factors a is the hyperfine coupling constant H is the external magnetic field while I and S are the nuclear and electron spin operators. The electronic g factor and the hyperfine constant are actually tensors, but for the hydrogen atom they may be treated, to a good approximation, as scalar quantities. 

The resonance expression relating the magnetic field and energy (frequency) as seen in equation 3.16, AE = hv = g B R, has its analog for hyperfine interactions written as equation 3.19, where A is the hyperfine coupling constant in Hz ... 

The hyperfine interactions of proton nuclei with the unpaired electron in a radical splits the proton signals into doublets with large coupling constants (up to 100 MHz) in comparison to the J values of 10 Hz observed in NMR spectroscopy. For the small magnetic field employed in an ESR spectrometer, all uncoupled protons absorb at effectively the same rf. The ENDOR spectmm appears as a series of doublets with lines spaced equally upheld and downfield from the expected absorbance of an uncoupled proton. 

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