Scalar Spin Couplings

Spin-spin coupling (scalar coupling) independent on Ho small values yes, but not dominant = 200 Hz... 

If there is indirect spin-spin coupling (scalar) coupling between two spins I and S and if the relaxation of nucleus S is short due to other interactions, quadrupolar interactions, it may cause relaxation for for nucleus I, known as scalar relaxation, proposed first by Solomon and Bloembergen [80] and observed it for hydrogen fluoride. 

The coupling mechanism we discussed in this section is known under the following alternative names Spin-spin coupling, Scalar coupling, J-coupling, or Indirect coupling. 

Magnetic nuclei interact not only with applied and induced magnetic fields, but also with one another. The result, for molecules in liquids, is a fine structure known as spin-spin couplings scalar coupling or J-coupling illustrated by the spectrum of ethanol in Figure 2. 

The water nucleus chosen also has an impact on relaxation data. Proton relaxation is affected by chemical exchange and cross-relaxation, 2H by chemical exchange, and lyO by proton-exchange broadening (scalar spin-spin coupling between lH and lyO nuclei affects T2, but not 7)) (Glasel,... 

Shortest-range interactions (over molecular distances of up to a few bonds away) examined by magnetic resonance are those that cause effects such as chemical shift, spin-spin coupling (also called scalar or J ... 

While the terminology scalar relaxation of the first kind concerns J modulation (J spin spin or scalar or indirect coupling constant) by exchange phenomena, the usual example of the second kind is a spin 1/2 nucleus (7), J coupled to a fast relaxing quadrupolar nucleus (S) with relaxation times Tj and Tf (and spin number /s)- The relevant interaction is of the form... 

Solomon and Bloembergen (21,22) formulated a similar expression for the interaction between the two spins being scalar (J-coupling) rather than... 

A more general formulation of relaxation theory, suitable for systems with scalar spin-spin couplings (J-couplings) or for systems with spin quantum numbers higher than 1/2, is known as the Wangsness, Bloch and Redfield (WBR) theory or the Redfield theory 17). In analogy with the Solomon-Bloembergen formulation, the Redfield theory is also based on the second-order perturbation approach, which in certain situations (not uncommon in... 

An electron spin can relax by coupling with a neighboring electron spin. Therefore, when a paramagnetic metal ion interacts with a second paramagnetic metal ion, the electron relaxation rates of the two metal ions may be dramatically affected. If Si and S2 are the two spins coupled by a scalar interaction, new spin levels will be established due to the interaction, with total S varying in unitary steps from Si — S2I to Si + S2. The energies of these spin levels are given by )... 

SCALAR SPIN-SPIN COUPLING THROUGH DIHYDROGEN BONDS AS EVIDENCE OF THEIR PARTLY COVALENT CHARACTER... 

SCALAR SPIN-SPIN COUPLING THROUGH DIHYDROGEN BONDS... 

Properties of the selective pulses are used therefore twofold in such experiments. Firstly, a selective pulse selectively perturbs the selected spin and the perturbation is distributed in the course of the experiment among the coupled spins, depending on the type of coupling (scalar, dipolar) and depending on the type of exchange mechanism (polarization transfer, cross polarization or cross relaxation). Secondly, the phase (selective 90° pulse) or the frequency (selective 180° pulse) of the selective pulse serve to label the response of both the selected and the residual coupled spins as positive or negative. 

Table 3. Non-relativistic and Scalar ZORA Hg-C spin-spin couplings (in Hz) calculated at the GGA levels Experimental values are also shown, taken from the same paper...

It should be remarked that this is the first practical implementation of the calculation of spin-spin couplings involving heavy atoms applicable to medium sized molecular systems. Formerly, Khandogin and Ziegler101 developed a frozen core scalar relativistic approach in combination with the non-relativistic FC and PSO operators, but the quality of results thus obtained is poorer than those obtained with ZORA. 

---