Precession inducing

Treffers, M.A. and Korving, J. (1986). Precession induced modulation of fluorescence, J. Chem. Phys., 85, 5076-5084. 

Figure 4-9. (Ai Precessing moment vectors in field tfo creating steady-state magnetization vector Afo. with//i = 0. (B) Immediately following application of a 90° pulse along the x axis in the rotating frame. (C) Free induction decay of the induced magnetization showing relaxation back to the configuration in A.

The quantity of interest is the precession of the components perpendicular to B0 that are measured in the experiment by induced voltage in the coil, which is subsequently amplified and demodulated. We can write them either as individual components Mx, M, or by a vector M+, which combines both of them. In the static field, the precession about B0 occurs with the Larmor frequency w0 = /B0. If we neglect those processes which dampen the amplitude of the rotating transverse magnetization as precession proceeds, this already describes the frequency that we pick up with our receiver coil, and it is the third and perhaps the most important of our three fundamental equations of NMR ... 

In strongly coupled systems, it is not possible to eliminate chemical shifts by refocusing nor is it possible to describe the evolution in terms of an effective Hamiltonian.44 A 90° or a 180° pulse leads to coherence transfer between various transitions, and a multitude of new effective precession frequencies may appear in the F1 dimension. A detailed analysis shows artefacts resulting of strong coupling induced by the 180° pulse applied on the H channel can be efficiently removed by applying a LPJF before acquisition.42 Likewise, artefacts present in HMBC with a terminal LPJF are suppressed by an LPJF in the beginning of the sequence as in conventional HMBC. 

It is clear that for a substance with dielectric loss, e. g. water and the alcohols, the molecules do not perfectly follow the oscillations of the electric field. For media without dielectric loss, and for the same reasons as under static conditions, the strength of the electric field cannot induce rotation of all polar molecules but, statistically, for a small part only (less than 1%). This means that all the molecules oscillate around an average direction (precession motion), as shown by Fig. 1.5. 

Vortex-induced separator, 22 62-63 Vortex-induced vibration, 11 756 Vortex meters, mass flowmeters, 20 681 Vortex patterns, 11 755 Vortex precession meters, 11 668 Vortex shedding, 11 756 Vortex shedding meters, 11 668-669 Vortices, superconductor, 23 824-825 Voyage charters, 25 327 VP Sandoflam 5085, 11 491 V-type inks, 14 326 Vulcanizable silicone rubber, 25 129 Vulcanizable silicones, properties and applications of, 22 594-595, 596-597 Vulcanizates EPDM, 10 713 EPM/EPDM, 10 715 ethylene-acrylic elastomer, 10 698,... 

The SIN defined by Equation 7.6 for a given NMR resonance is proportional to the square of the nuclear precession frequency (mo, rad/s), the magnitude of the transverse magnetic field (Bi) induced in the RE coil per unit current (/), the number of spins per unit volume (Ns), the sample volume (Vs), and a scaling constant that accounts for magnetic field inhomogeneities. The SIN is inversely proportional to the noise generated in the RE receiver and by the sample (Vnoise) as defined by the Nyquist theorem,... 

Note 4 The director precession in a chiral nematic mesophase is spontaneous and should be distinguished from an induced twisted structure produced by a mechanical twist of a nematic mesophase between confining surfaces. 

In pulsed NMR, the magnetic field is turned on for the time necessary to rotate the magnetization vector into a plane called the 90° rotation or 90° pulse. The field is turned off and the magnetization vector rotates at a nuclear precession frequency relative to the coil. This induces an NMR signal that decays with time as the system returns to equilibrium. This signal is called the free induction decay (FID). 

If the bullet is spun clockwi se by the rifling, the wind force tending to push the nose up induces a precession, and the nose of the bullet is turned to the right of the trajectory as viewed from die gun. This in tum produces a further precession, and the nose rises... 

The radiofrequency, or frequency with which the spin vector rotates around the central axis Oz that induces a change in states, is called the Larmor precession frequency. The Irish physicist Larmor, whose work preceded NMR, has shown independently that to, the angular rotation frequency around a central axis Oz, has a value of ... 

At resonance, the magnetization vector M precesses about the vector B, i of the alternating field according to eq. (1.34). As a result, a component of transverse magnetization My.j rotates in the x y plane at the Larmor frequency v0. If a receiver coil is placed in the x y plane, the rotating magnetic vector Myj induces an electromotive force measurable as an inductance current. This process is called nuclear induction [5, 8]. The orientation of the coil axis will affect the phase relative to B1 i but not the magnitude of the induction current. 

Snider is best known for his paper reporting what is now referred to as the Waldmann-Snider equation.34 (L. Waldmann independently derived the same result via an alternative method.) The novelty of this equation is that it takes into account the consequences of the superposition of quantum wavefunctions. For example, while the usual Boltzmann equation describes the collisionally induced decay of the rotational state probability distribution of a spin system to equilibrium, the modifications allow the effects of magnetic field precession to be simultaneously taken into account. Snider has used this equation to explain a variety of effects including the Senftleben-Beenakker effect (i.e., is, the magnetic and electric field dependence of gas transport coefficients), gas phase NMR relaxation, and gas phase muon spin relaxation.35... 

---