Electron Diamagnetism

Much less is known about the charge states of muonium in silicon that are not neutral. The most likely ones of these are the positive and negative charge states, Mu+ and Mu. Both would have an even number of electrons and hence would quite likely be electronically diamagnetic. They presumably contribute to the p.SR line, usually labelled p+, which occurs at the Larmor frequency of a bare muon. Little else is known about these charge states other than that at high temperatures at least one of them is formed from neutral muonium, Mu and Mu. ... 

Paramagnetism, the attraction of a molecule to a magnetic field, is due to the presence of unpaired electrons. Diamagnetism, the repulsion of a molecule from a magnetic field, is due to the presence of paired electrons. 

Table 6. Radon core and localized 5 f electrons diamagnetic correction for light actinide ions...

The pairing of electrons in the MOs can manifest itself in certain physical properties of the molecule. Paramagnetism results when there are unpaired electrons in the molecular orbitals. Paramagnetic molecules magnetize in magnetic fields due to the alignment of unpaired electrons. Diamagnetism occurs when there are all paired electrons in the MOs. We will revisit these properties in Chapter 6. 

These variations result, in a molecule, from the nucleus being surrounded by electrons which also interact with the magnetic field. The movement of the electrons in their orbits is altered such that they create a secondary magnetic field opposing the applied magnetic field. This is electron diamagnetism. It is as if the electrons were protecting the nuclei from the effect of Bq. This secondary field is proportional to Bq and can be expressed as follows ... 

This is normally found for Be +, Mg + and higher charge cations including some of the electronically diamagnetic transition metal ions, lanthanides and actinides. Paramagnetic transition metal cations can be studied using or D resonance. 

This electronic Diamagnetic Shielding operator contributes to the ESR g-tensor. 

Cemusak et al have used the Coupled HF method to study ring currents in six cyclic isomers of (CH)2B2N2. Correlated calculations show that all six have planar structures and Tt-electron diamagnetic ring currents. The nuclear shielding produced by the ring current is compared with that of benzene. 

Fig. 3.2. Electronic, paramagnetic volume susceptibility of liquid cesium (derived from data of Preyland, 1979) as a function of reduced density p/p. Total susceptibility data are corrected for ionic diamagnetism and, for the liquid state, are corrected for conduction electron diamagnetism using theories of I nazawa and Matsudawa (1960) solid line) and Vignale et al. (1988) dot-dash line). Dashed line represents Curie law susceptibility along liquid-vapor coexistence curve, calculated for monovalent, atomic cesium. Note the deviation from Curie law behavior of the vapor for p/p. 2.

Here, e and m refer to the charge and mass of the electron, c is the velocity of light, N the Avogadro number and the expectation value (mean value) of the square distance of the electron from the nucleus. According to Eq. (11), diamagnetic susceptibilities should be independent of temperature which is observed in practice to a good approximation. Since all substances contain electrons, diamagnetism is an inherent property of all atomic and molecular systems. 

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