Zeeman field

B (the Zeeman field) must be made to commute rapidly between several predefined values, such as the polarization field Bp, the relaxation field and the acquisition field Ba-... 

Zeeman effects 393 Zeeman energy 111, 113 Zeeman field 411 Zeeman Hamiltonian 46 Zeeman interaction 59, 79, 248 Zeeman limit 49-50 Zeolite 307, 310... 

Figure J A simulated H pulsed NMR spectrum of an idealized chemical species H Hx, nominally taken at fixed carrier frequency v0=500.0... MHz. Here the Zeeman field B is deemed to be kept fixed at 11.74334 T, and Fourier transformation yields the spectrum. There are 6 (A) and 6 (X) distinct lines of appreciable intensity (12 and 14 transitions, respectively), with each individual line depicted as a Lorentzian with half-width 0.1 Hz.

The nuclear hyperfine interaction splits the paramagnetic states of an electron when it is close to a nucleus with a magnetic moment. For a random orientation of spins and nuclei, the tensor quantities in Eq. (4.11) are replaced by scalar distributions, and the resonance magnetic field is shifted from the Zeeman field // by... 

We now calculate the perturbation to the Zeeman field due to the quadrupolar interaction by means of average Hamiltonian theory.This is accomplished by transforming TYq to the Zeeman interaction frame and then applying the spherical tensor rotation properties to the spin elements 72,The resulting quadrupolar Hamiltonian TTq in the rotating frame is given by ... 

Fig. 1. The FC principle for measurements of the longitudinal spin relaxation time T at different Larmor frequencies (i ) or Zeeman fields (Bq), i e. of the relaxation dispersion 7 ](t ) or The upper diagram illustrates the Bo t) cycle with finite...

In FC experiments, where the external Zeeman field, 5o (with selectable... 

Jeener and Broekaert introduced, in 1%7, a three-pulse B,(r) sequence to measure the relaxation time Tm of the dipolar order of / = 1 spin systems in the presence of a conventional high Zeeman field, Bq, which is based on the decay time of the so-called Jeener echo . It was later extended by Spiess and Kemp-Harper and Wimperis to study in a similar way the quadrupolar order in / a 1 systems. The appearance of a Jeener echo depends upon the existence of interactions that are not averaged out by molecular motions on the considered time scale. The method has become of great importance in recent relaxation studies, in particular of liquid crystals because, in standard spin relaxation theories, it provides a power l means to separate and analyse the spectral densities / v) and /2) j. i4,is,2025 ggg... 

Although the initial measurements of ODMR 86-88) were made in the conventional manner, (fixed microwave frequency source and variable externally-applied Zeeman field) nearly all measurements on the aromatic amino acid triplet states have been made at zero applied field using a variable frequency microwave source. Consequently, we will focus on the zero-field experimental method in this section. 

The second diagnostic study made use of the Zeeman effect, observed when a small magnetic field was applied parallel to the ion beam direction. For almost every line in the spectrum a Zeeman splitting could be observed figure 10.73 illustrates a particularly simple example, where the six-line Zeeman pattern shows conclusively that the resonance must arise from a J = 3/2 3/2 transition. Effective g factors are obtained for both levels, providing valuable additional information which we shall discuss in detail later. It is important to know the microwave mode involved in a particular resonance because this determines the nature of the Zeeman components. The transitions are electric-dipole allowed, and if the Zeeman field is parallel to the... 

A new adiabatic double quantum polarisation transfer experiment has been proposed, which is an adiabatic variant of the POST-C7 experiment. A continuous variation of the phase increment between pulses in this experiment leads to the introduction of a fictitious Zeeman field that allows for an adiabatic passage through the recoupling condition. This results in a chemical shift offset-compensated adiabatic experiment, which leads to an efficient and broadbanded polarisation transfer or to a double quantum excitation. 

Su is the component of S along the effective Zeeman field direction u = gl/. ... 

The reason here is that the l N nucleus has a small magnetic moment, which is hard to drive by r.f. fields, the difficulty being compounded in the case of frozen solution samples by line broadening due to the l N nuclear quadrupolar coupling. Echo envelope modulation effects are, on the other hand, quite easy to see for nuclei with small moments. For the simple case of an I = 1/2 nucleus weakly coupled to an S = 1/2 electron, it can be shown that the modulation depth is independent of the nuclear moment and depends only on the ratio between the Zeeman field and the local field at the nucleus due to the electron.15 Breadth of the shfs line is, moreover, not a serious obstacle to detection, provided that at least one modulation cycle can be seen in the echo envelope. 

Figure 5. Four-level hyperfine diagram illustrating manifold with sign of nuclear hyperfine coupling opposite that of nuclear Zeeman term, making it possible to adjust the Zeeman field so that the spin manifold levels cross.

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