A possible interaction effect in graphite

It is shown that there appears to be a significant correlation between one of the supposed minority carrier de Haas-van Alphen frequencies in graphite and the difference of the majority electron and hole frequencies.     

Microwave plasma generation by end-on and side-on irradiation in the pressure range 0.1–10 mTorr of hydrogen

This paper describes investigations of hydrogen plasmas produced by mean of linearly polarized microwaves (f=2.45 GHz,P ₀=2.2–5.0 kW). A superimposed uniform and stationary magnetic field \(\vec B_z \) is tuned in most of the experiments to the electron cyclotron resonance. The RF is coupled to the plasma by different antennae. A conical horn is used for end-on irradiation (wave vector \(\vec k\parallel \vec B_z \) ). With regard to toroidal discharge geometries the side-on irradiation \(\vec k \bot \vec B_z \) is of particular interest. For this purpose two newT-shaped antennae were developed. In the pressure range investigated the plasma produced by the microwaves fills up the whole discharge vessel (l=200 cm,V≈10⁴cm³). The electron densities are in the range between 2.5 · 10¹⁰ and 1.5 · 10¹¹ cm^?3 and the electron temperatures between 1.2 and 5.0 eV. The plasma produced by side-on RF irradiation \((\vec k \bot \vec B_z ,\vec E\parallel \vec B_z )\) is used as a pre-ionization plasma for aZ-pinch discharge. The degree of ionization obtained in this way is ?5%. The optimum conditions for this type of preionization are evaluated from density measurements at higher cyclotron harmonics.     

Polyferrocenylenes by oxidative coupling of 1,1′-dilithioferrocene with Cu2+ Ion(1)

Summary The oxidative coupling of 1,1 -dilithioferrocene (chelated withN,N,N,N-tetramethylethylenediamine) in the presence of Cu^II halide (Cu²⁺Li=1–1.5) in ether solvents at –70 to 110° gives 30–45% yields of polyferrocenylene. Still higher yields of coupling products result from reactions in which oxidative coupling is paired with thermal coupling,i. e. C-C bond formation through thermal decomposition of organocopper(I) intermediates in the absence of external oxidant (Cu²⁺Li=0.5). Number-average molecular masses of the highest fractions of linear products (2) as separated in the primary work-up process are in the 1500–3400 range, and fractionating precipitation results in subfractions with M_n as high as 5000. Cyclization of dinuclear intermediates, producting up to 10% of [0,0] ferrocenophane (bisfulvalenediiron), competes in all experiments with linear propagation. Experiments conducted with Cu^I halides under conditions leading exclusively to thermal coupling provide even higher conversion to the ferrocenophane (up to 25% yields) at the expense of linear condensation products. Spectroscopic features of the polyferrocenylenes are discussed. In the linear compounds with ¯M_n>800, i.r. absorptions and p.m.r.'s are remarkably invariant with the degree of polymerization, as are the electronic absorption maxima. This shows, in confirmation of earlier reports, that there is insignificant resonance interaction between the cyclopentadienyl rings in the ferrocene system and hence little, if any, electronic delocalization along the polymer chain of heteroannularly interlinked polyferrocenylene structures.     

Metallocene Polymers XXVI. Isomeric terferrocenyls in the polyrecombination reaction of ferrocene

A re-examination of the oligonuclear by-products arising in the previously reported polyrecombination reaction of ferrocene in the presence of tert-butyl peroxide has revealed the presence of an additional trinuclear compound, m.p. 198–200°, to which the structure of 1,2-diferrocenylferrocene (1,2-terferrocenyl) is ascribed on the basis of spectroscopic and other evidence. The compound is found to be identical with an authentic sample synthesised by other workers. Separation from other oligonuclear ferrocenes is accomplished by column chromatography. This result, coupled with the firm identification of the remaining two possible terferrocenyl isomers of the previous study as 1,3-terferrocenyl and 1,1′-terferrocenyl, necessitates a reassignment of the compound, m.p. 260–265°, which had tentatively been identified in that study as a terferrocenyl.