Static spinning

K. Binder, P. C. Hoehenberg. Phase transitions and static spin correlations in Ising models with free surfaces. Phys Rev B 6 3461-3487, 1972. 

Without spin refocusing, the simulations show that R2 reaches a plateau for diameters above 0.02 pm. The corresponding maximum relaxation rate of about 100 s is predicted by the Static Dephasing Regime (SDR) model 22, 23), which assumes that, as depicted above, transverse relaxation is only attributed to differences in precession frequencies of static spins. The relaxation rate is then given by ... 

This model is close to the SDR. However, the SDR only deals with static spins, so that relaxation, more specifically the first-order effect we investigate, is automatically canceled by the refocusing pulses. On the contrary, our model accounts for irreversible dynamics the randomness of the jumps from... 

The solvated electron is responsible for a single, extremely narrow, structureless spin resonance line in the dilute solutions with a g value of 2.0012. Integration of its intensity gives a static spin susceptibility tending towards the... 

In order to analyze these data, the frequency shift of geffectivecan be calculated by averaging over all orientations the anisotropic shift derived from a static spin Hamiltonian [67]. This treatment is based on the assumptions that molecular motion neither changes the spin precession rate nor perturbs the states and, thus, that the center of gravity of the spectrum is invariant even in presence of some motional averaging. For the allowed 11/2) <-> <-l/2 transition under perturbation theory, with expressions valid up to the third order, this shift is given by [47] ... 

Static Spin-Singlets Stabilized by Jahn-Teller Distortions. 179... 

Fig. 2.6. Temperature dependence of the static spin susceptibility for (TMTSF)2AsFe. The inset shows the exponential decrease of the susceptibihty in the b direction below Tmi- Prom [55]...

Static spin echo decay spectroscopy also forms the basis for the measurement of magnetic dipole-dipole interactions between two unlike nuclei I and S. While this interaction is refocused by the Hahn spin echo, it can be recoupled by applying a 7i-pulse to the S-spins during the dipolar evolution period [12]. This manipulation inverts the sign of the heterodipolar Hamiltonian, and thereby interferes with the ability of the Hahn spin echo technique to refocus this interaction. The corresponding pulse sequence, termed SEDOR spin echo double resonance) shown in Fig. 4, compares the I-spin echo intensity as a function of dipolar evolution time (a) in the absence and (b) in the presence of the ti(S) pulses. Experiment (a) produces a decay F(2ti)/Fo, which is dominated by homonuclear dipole-dipole interactions, while experiment (b) results in an accelerated decay, reflecting the contribution from the heteronuclear I-S dipole-dipole interaction, which is now re-introduced into the spin Hamiltonian. For multi-spin systems, a Gaussian decay is expected ... 

FIGURE 5 Solid-state proton spectra of (L)-alanine, showing the differences between spectra acquired in static, spinning, and CRAMPS modes. All 500 MHz spectra were acquired at ambient conditions. 

A very effective signal sensitivity enhancement scheme for MQMAS as well as for MAS is the DFS introduced by the group of Kentgens.The underlying principles of DFS and FAM are similar and they have been exphcitly dealt with already. In a nutshell, a cosine amplitude modulated RF carrier wave irradiates the sample at two frequencies, namely, ioq -F w, and aio — Larmor frequency of the spins and is the frequency of modulation. This means that if satellite transitions of a static spins-1 system will be simultaneously... 

At any temperature, x(T)/Xc gives the effective number of free spins and is related by the fluctuation-dissipation theorem to the sum of all static spin correlations. The complicated X(T)/Xc behavior in Fig. 17 thus points to disordered exchanges in the power-law regime below 40 °K the flat region 40 < T < 140 K suggests that some 8% are essentially free and follow the Curie law, Eq. (7) the T > 140 K regime... 

Finally, we mention double-resonance techniques tailored to study the de-focusing process on rotational echoes generated by MAS rather than on static spin echoes. / otational Spin-Echo Double /fesonance (REDOR) [115], Notary Resonance decoupling (RRR) [116], and Transferred-Echo Double desonance... 

One theory which has been successfully applied to the magnetic properties of R-compound alloys containing non-S-state R-ions is the theory of random magnetic anisotropy (RMA) of Harris et al. (1973). This has been used to calculate the magnetoresistivity of amorphous alloys exhibiting RMA. Bhat-tacharjee and Coqblin (1979) first obtained the static spin-spin correlation function of the RMA model by using a self-consistent two-spin cluster approximation. The quasi-elastic approximation of de Gennes and Friedel is then... 

In the static spin process, a few volumes of solution is dropped onto the substrate and allowed to spread until it covers most of the surface. Once the liquid has reached a specified diameter the chuck is accelerated to a predetermined speed, on the order of 20,000 rpm. 

The ground subspace of each molecule is isomorphic to a spin-1/2 particle. Our goal is to obtain an effective spin-spin interaction between two neighboring molecules. Static spin-spin interactions due to spin-rotation and dipole-dipole couplings do exist but are very small in our model Hvdvj(r) = d /2Br ) [l + (y/45) (l - -4Si S2/3 — 2Sj52)]. familiar... 

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