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103.
Dedkov YS Laubschat C Khmelevskyi S Redinger J Mohn P Weinert M 《Physical review letters》2007,99(4):047204
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. 相似文献
104.
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. 相似文献
105.
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. 相似文献
106.
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). 相似文献
107.
Hanns M. Weinert Christoph Wlper Julia Haak George E. Cutsail III Stephan Schulz 《Chemical science》2021,12(42):14024
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. 相似文献
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Mahendra K. Sharma Sonia Chabbra Christoph Wlper Hanns M. Weinert Edward J. Reijerse Alexander Schnegg Stephan Schulz 《Chemical science》2022,13(43):12643
Modulating the electronic structures of main group element compounds is crucial to control their chemical reactivity. Herein we report on the synthesis, frontier orbital modulation, and one-electron oxidation of two L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl 2a, Br 2b; L = HC[C(Me)N(Ar)]2, Ar = 2,6-i-Pr2C6H3). Photolysis of L(Cl)GaPCO 1 gave [L(Cl)GaP]22a, which reacted with Me3SiBr with halide exchange to [L(Br)GaP]22b. Reactions with MeNHC (MeNHC = 1,3,4,5-tetramethylimidazol-2-ylidene) gave the corresponding carbene-coordinated complexes L(X)GaPP(MeNHC)Ga(X)L (X = Cl 3a, Br 3b). DFT calculations revealed that the carbene coordination modulates the frontier orbitals (i.e. HOMO/LUMO) of diphosphenes 2a and 2b, thereby affecting the reactivity of 3a and 3b. In marked contrast to diphosphenes 2a and 2b, the cyclic voltammograms (CVs) of the carbene-coordinated complexes each show one reversible redox event at E1/2 = −0.65 V (3a) and −0.36 V (3b), indicating their one-electron oxidation to the corresponding radical cations as was confirmed by reactions of 3a and 3b with the [FeCp2][B(C6F5)4], yielding the radical cations [L(X)GaPP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 4a, Br 4b). The unpaired spin in 4a (79%) and 4b (80%) is mainly located at the carbene-uncoordinated phosphorus atoms as was revealed by DFT calculations and furthermore experimentally proven in reactions with nBu3SnH, yielding the diphosphane cations [L(X)GaPHP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 5a, Br 5b). Compounds 2–5 were fully characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), and compounds 4a and 4b were further studied by EPR spectroscopy, while their bonding nature was investigated by DFT calculations.Carbene-coordination allowed for one-electron oxidation of diphosphenes [LGa(X)P]2 to P-centered radicals cations 4a (X = Cl) and 4b (X = Br), in which the unpaired spin mainly reside at the carbene uncoordinated P-atoms. 相似文献
110.