Contribution of the conduction electrons

The paramagnetism of the conduction electrons, not observable by ESR, can however be detected by a measurement of the magnetic susceptibility. In the region of metalhc conductivity, one observes in the contribution of the conduction electrons a nearly temperature-independent Pauli susceptibility, well known from metals. In those crystals which undergo a Peierls transition and become semiconductors or insulators at low temperatures, the Pauli susceptibility is transformed into a Curie-law behaviour. The susceptibility then increases with further decreasing tern-... 

The contribution of the conduction electrons to the electronic magnetisation is that of Pauli paramagnetism in a classical 3-d metal ... 

Ray, D.K., 1971, in Contributions of the Conduction Electrons to the Crystalline Electric Field in Rare Earth Metals, Rare Earths and Actinides, Inst. Phys. Conf. No. 3, (Durham, England) (Institute of Physics, Bristol) p. 15. 

Along the easy <100> axis the magnetic moment is actually 0.62n per Pu ion. Thus the difference with the neutron value (O.TT/ts) is not appreciable, and the possible contribution of the conduction-electron polarization would be only O.IS/xb, a reasonable value. The hysteresis loop is extremely broad. Due to large anisotropy the Bloch... 

Mossbauer measurements yield a magnetic moment of 0.75 b> the same value as obtained from neutron diffraction experiments. Since the magnetic value is unambiguously 0.67/tB the contribution of the conduction electrons should be about... 

The shape of the angular correlation distribution profile is a superposition of two contributions. Annihilation of the positron with the conduction electrons results in a contribution that has the approximate shape of an inverted parabola, while the contribution of the high-momentum core electrons is reflected in a broad, Gaussian-like distribution. When the core electron density is reduced, as is the case for a positron trapped in a vacancy, the contribution of the conduction electrons is enhanced and a narrower distribution is measured. Therefore, changes in the shape of the angular correlation distribution profile reflect a reduction in annihilation with core electrons [127]. 

Step can be a decrease of the Pauli-like contribution of the conduction electrons, but the second one is more probably associated with a reduction of temperature-independent paramagnetism of the inorganic polymeric chains. Just below the second transition a residual value of 1.8 x lO " emu/mol is observed, probably indicative of a temperature-independent paramagnetism, and upon further cooling an increase of the susceptibility due to a Curie tail is observed. This tail shows an increase as with a = 0.6, an exponent that is indicative of disorder [98—100], most probably associated with the solvent. Since this compound is EPR silent no further indications on the origin of the observed susceptibility can be taken from these data alone. 

As described above, quantum restrictions limit the contribution of the free electrons in metals to the heat capacity to a very small effect. These same electrons dominate the thermal conduction of metals acting as efficient energy transfer media in metallic materials. The contribution of free electrons to thermal transport is very closely related to their role in the transport of electric current through a metal, and this major effect is described through the Wiedemann-Franz ratio which, in the Lorenz modification, states that... 

The contribution of the valence band does not change when the overpotential is varied, since it remains practically completely filled. In contrast, the contribution of the conduction band decreases exponentially with rj (or increases exponentially with —rj) because of the corresponding change of the density of electrons. In summary, the current densities via the two bands are ... 

In solid-state NMR [1,51-64], the magnetic coupling between the fullerene anions has to be taken into accoimt. In the case of metal intercalated fullerides that have metallic properties a contribution from the conduction electrons must be added, a phenomenon called the Knight shift . Even if this additional shift affects the C-chemical resonance, the correspondence between extended and discrete systems of comparable Cjq oxidation state is quite close [1]. 

Kaiser et al.119 have studied 19F NMR in (Pyrene)i2(SbFg)7 cation salt. The rotational motion of those SbFg anions of this salt can be best discriminated by the analysis of the temporal evolution of the 1H Overhauser shift of the conduction electron ESR line. Temperature dependence of the Overhauser shift detected proton-SLR rate recorded at 9.46 GHz electron spin and 14.4 MHz proton NMR frequency. It is important to note that the proton relaxation reflects only the low temperature BPP-peak of SbFg anion rotation, in addition to conduction electron contribution. This salt undergoes a 3D-ordered Peierls transition at 113 K, which is due to the freezing of the anion motion. 

The absence of localized states is clearly supported by the small, Pauli-type paramagnetism of Lal2, 0 db 5 and (30 dz 10) X 10 e.m.u. mole at 299° and 78°K., respectively. Values of this magnitude are characteristic of metals where they are (ideally) associated with the Pauli spin paramagnetism of the conduction electrons. In the present case the results of correction for the diamagnetic contribution of the iodide ions in LaL [ (104 dz 5) and (134 dz 10) X 10 , respectively] are again remarkably (and probably fortuitously) close to those for the metal (113 and 139 X 10" ) (22). 

The /- F behavior demonstrates that holes are involved in the anodic dissolution reactions the question arises, however, whether charge transfer occurs exclusively over the valence band. A straightforward way to investigate this problem is by comparing the number of photons absorbed in an n-type photoanode to the number of electrons flowing through the external circuit. This procedure has been used by Kohl et al. [33], and its results indicate a non-negligible contribution of the conduction... 

---