Positive g-shift

For these and other reasons it seems improbable that H2S" is a correct formulation for either of these radicals. Possible alternatives include H2S+, isoelectronic with PH2, and species such as H2S2", H2S2 or more complex polysulfide radicals. The radical H2S+ is a possible candidate for the species in alkali halide crystals (56), which apparently contains only one sulfur atom, except that some restricted rotational motion would need to be invoked to explain the equivalence of the two protons. Rotation within the molecular plane would achieve this, and would also account for the form and magnitude of the anisotropic proton coupling. The 33S tensor is also accommodated reasonably well, as also is the positive g-shift. However, the very large value for Ag is more difficult to reconcile with this formulation. 

Amorphous Gd, , Al films prepared by sputtering were investigated by Jamet and Malozemoff (1978). In the paramagnetic regime the alloys of the concentrations X = 0.19, 0.44 and 0.63 were found to have a small positive g shift (Ag = 0.006 + 0.004). This is in contrast with the negative value of Ag observed earlier in crystalline Gd-Al compounds (see for instance Davidov et al., 1973). Jamet and Malozemoff analysed their data in terms of the RKKY model and conclude that the... 

Shaltiel et al. (1964a) noticed that Sm produces a positive g-shift for the Gd resonance in Pdo.96Gdo.02Smo.02> opposite to what is expected from a simple model. They pointed to the fact that the temperature-independent van-Vleck part of the susceptibility should produce an additional positive shift. Malik and Vijayaraghavan (1975) confirmed these results and provided more detailed information. They found that the distance between the H5/2 ground state and the H7/2 first excited state of Sm " " is so small that the van-Vleck terms contribute appreciably and as a consequence the z-component of the lanthanide spin changes sign. 

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