Stark effect negative

In the field of FTIR of electrode surfaces, it is well known that the C-0 vibrational frequency, Vco> decreases when the electrode potential becomes more negative. This variation of the vibrational frequency with electrode potential is referred to as the vibrational Stark effect. The Stark effect can now be considered in the context of our NMR... 

In order to understand which is the principal parameter involved in the spatial overlap, let us consider the Nd " free-ion states (fig. 31). Cross-relaxation can take place only if the energy released by ion S(Nd ) is about equal to the energy which can be accepted by ion A(Nd), For two near but free ions the energy difference (e2 - ei) being negative, such transfer could not take place. For ions in a crystal, the Stark effect can provide the resonance condition . E2M - im = 0 which, for phonon-assisted transfers, can be extended to 0. 

The same argument applies to the Stark effect in a strong electric held. In a weak field each term determined by j splits in components characterised i = j, j - 1,. (negative terms add nothing new). In a strong field the multiplet characterised by n, Z, s splits in components characterised by t( ss i, Z - 1,... and each of these obtains a structure through s s, s — 1,... 

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