YCo2: intrinsic magnetic surface of a paramagnetic bulk material

Here we report on results of a spin-resolved photoelectron spectroscopic (SRPES) study of YCo2 thin films (150 A-thick) grown on a W(110) substrate. The films were prepared by co-deposition of stoichiometric amounts of Y and Co onto a clean W surface followed by thermal annealing leading to (2x2) overstructure with respect to W(110) in the low-energy electron diffraction pattern indicated formation of a structurally ordered YCo2(111) surface. While no clear spin asymmetry was observed for bulk-sensitive SRPES data taken at hnu=1253.6 eV, the more surface-sensitive SRPES data obtained at hnu=21.2 eV photon energy revealed a clear spin-asymmetry probing the validity of the recent theoretical prediction.     

Synthesis and crystal structure of a germanium(II) calix[6]arene containing unusual diamidosilyl ether groups

The reaction of Ge[N(SiMe₃)₂]₂ with calix[6]arene furnishes a novel macrocyclic product having two divalent germanium atoms incorporated into a Ge₂NO rhombus which contains a μ₂-oxygen atom and a μ₂-NH₂ group. The crystal structure of the product indicates the presence of a conformationally rigid molecule where three of the six oxygen atoms of the calix[6]arene are bound to the germanium atoms while the remaining three have been converted into –OSiMe₃ or unusual –OSi(H)(NH₂)₂ groups. Spectral (¹H, ¹³C, and ²⁹Si NMR) data in solution are consistent with the solid-state structure and indicate the germanium calix[6]arene retains its structure in solution.     

Choiceless Ramsey Theory of Linear Orders

Motivated by work of Erd?s, Milner and Rado, we investigate symmetric and asymmetric partition relations for linear orders without the axiom of choice. The relations state the existence of a subset in one of finitely many given order types that is homogeneous for a given colouring of the finite subsets of a fixed size of a linear order. We mainly study the linear orders 〈 ^α 2,< _{l e x} 〉, where α is an infinite ordinal and < _{l e x} is the lexicographical order. We first obtain the consistency of several partition relations that are incompatible with the axiom of choice. For instance we derive partition relations for 〈 ^ω 2,< _{l e x} 〉 from the property of Baire for all subsets of ^ω 2 and show that the relation \(\langle ^{\kappa }{2}, <_{lex}\rangle \longrightarrow (\langle ^{\kappa }{2}, <_{lex}\rangle )^{2}_{2}\) is consistent for uncountable regular cardinals κ with κ ^<κ = κ. We then prove a series of negative partition relations with finite exponents for the linear orders 〈 ^α 2,< _{l e x} 〉. We combine the positive and negative results to completely classify which of the partition relations \(\langle ^{\omega }{2}, <_{lex}\rangle \longrightarrow (\bigvee _{\nu <\lambda }K_{\nu },\bigvee _{\nu <\mu }M_{\nu })^{m}\) for linear orders K _ν ,M _ν and m≤4 and 〈 ^ω 2,< _{l e x} 〉→(K,M) ⁿ for linear orders K,M and natural numbers n are consistent.     

The influence of crucible moving on growth rate and perfection of SSD-GaP crystals

The influence of the crucible moving (lowering, rotation) during the SSD growth of GaP on the growth rate and the crystal quality is investigated. The crucible lowering leads to an improvement especially of the crystal quality characterized by the size of the single crystalline regions and by the homogeneity of the impurity incorporation. On the other hand, the crucible rotation yields no noticeable improvements (in the case of constant frequency) or a strong increase of the growth rate connected with a deterioration of the crystal quality (accelerated rotation).     

A contribution to the kinetics of crystallisation of GaP by SSD process

The influence of some important factors which appear during the synthesis of GaP by the SSD-Process have been comprehended, and their mathematical relationships determined. The model for the growth of crystallisation is valid only for some definite and selected moments. For long-time experiments the computation of the speed of crystallisation should be carried out step-by-step.     

Synthesis,structure and bonding nature of heavy dipnictene radical anions

Cyclic voltammetry (CV) studies of two L(X)Ga-substituted dipnictenes [L(R₂N)GaE]₂ (E = Sb, R = Me 1; E = Bi; R = Et 2; L = HC[C(Me)NDipp]₂; Dipp = 2,6-i-Pr₂C₆H₃) showed reversible reduction events. Single electron reduction of 1 and 2 with KC₈ in DME in the presence of benzo-18-crown-6 (B-18-C-6) gave the corresponding dipnictenyl radical anions (DME)[K(B-18-C-6)][L(R₂N)GaE]₂ (E = Sb, R = Me 3; E = Bi, R = Et 4). Radical anions 3 and 4 were characterized by EPR, UV-vis and single crystal X-ray diffraction, while quantum chemical calculations gave deeper insight into the nature of the chemical bonding.

Dipnictene radical anions [K(DME)(B-18-C-6)][{L(R₂N)GaE}₂] (E = Sb, Bi) were characterized by single crystal X-ray diffraction, EPR spectroscopy and quantum chemical calculations.