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61.
Control of the charge state of metal atoms on thin MgO films 总被引:1,自引:0,他引:1
Sterrer M Risse T Martinez Pozzoni U Giordano L Heyde M Rust HP Pacchioni G Freund HJ 《Physical review letters》2007,98(9):096107
The arrangement of single gold and palladium atoms deposited on the surface of a 3 monolayer thin film of MgO was investigated using low-temperature scanning tunneling microscopy. While Pd atoms are arranged in a random fashion, Au forms an ordered array on the surface. The long-range ordering as well as the scanning tunneling microscopy appearance of single Au atoms on a 3 monolayer thin MgO film can be explained by partial charge transfer from the substrate to Au atoms as predicted recently by density functional theory calculations [Phys. Rev. Lett. 94, 226104 (2005)10.1103/PhysRevLett.94.226104]. In contrast with that, Au atoms on a thick film were found to be essentially neutral. 相似文献
62.
Two alternative approaches for the calibration of the intramolecular nitrogen isotope distribution in nitrous oxide using isotope ratio mass spectrometry have yielded a difference in the 15N site preference (defined as the difference between the delta15N of the central and end position nitrogen in NNO) of tropospheric N2O of almost 30 per thousand. One approach is based on adding small amounts of labeled 15N2O to the N2O reference gas and tracking the subsequent changes in m/z 30, 31, 44, 45 and 46, and this yields a 15N site preference of 46.3 +/- 1.4 per thousand for tropospheric N2O. The other involves the synthesis of N2O by thermal decomposition of isotopically characterized ammonium nitrate and yields a 15N site preference of 18.7 +/- 2.2 per thousand for tropospheric N2O. Both approaches neglect to fully account for isotope effects associated with the formation of NO+ fragment ions from the different isotopic species of N2O in the ion source of a mass spectrometer. These effects vary with conditions in the ion source and make it impossible to reproduce a calibration based on the addition of isotopically enriched N2O on mass spectrometers with different ion source configurations. These effects have a much smaller impact on the comparison of a laboratory reference gas with N2O synthesized from isotopically characterized ammonium nitrate. This second approach was successfully replicated and leads us to advocate the acceptance of the site preference value 18.7 +/- 2.2 per thousand for tropospheric N2O as the provisional community standard until further independent calibrations are developed and validated. We present a technique for evaluating the isotope effects associated with fragment ion formation and revised equations for converting ion signal ratios into isotopomer ratios. 相似文献
63.
64.
J. C. van der Merwe W. J. Naudé R. Saayman J. W. Koen N. J. A. Rust 《Zeitschrift für Physik A Hadrons and Nuclei》1980,295(2):121-134
The spins and electromagnetic properties of levels up to 3,700 keV in51V were studied by means of inelastic proton scattering. Results are discussed with reference to the many-particle shell model using effective surface delta and realistic Kuo-Brown interactions. 相似文献
65.
Petradza M Akerlof C Chapman J Errede D Ken MT Meyer DI Neal H Nitz D Thun R Tschirhart R Abachi S Derrick M Kooijman P Price LE Repond J Sugano K Cork B Blockus D Brabson B Brom JM Jung C Ogren H Rust DR Baringer P Bylsma BG DeBonte R Koltick D Low EH McIlwain RL Miller DH Ng CR Shibata EI 《Physical review D: Particles and fields》1990,42(7):2180-2186
66.
Abachi S Derrick M Kooijman P Musgrave B Price LE Repond J Sugano K Waschbusch P Blockus D Brabson B Brom JM Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Ken MT Meyer DI Neal H Nitz D Thun R Tschirhart R Baringer P Bylsma BG DeBonte R Koltick D Low EH McIlwain RL Miller DH Ng CR Shibata EI Cork B 《Physical review D: Particles and fields》1989,40(3):706-711
67.
Jrg Saßmannshausen Jrg Rust Richard Goddard 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):e236-e237
The title compound, [Zr(C7H7)3(C15H17)], (I), crystallizes from light petroleum with two independent molecules in the asymmetric unit. Whereas in the parent molecule, Zr(η5‐C5H5)(CH2Ph)3, all three Zr—CH2Ph angles are equal, in (I), they differ significantly. In spite of their different environments, both independent molecules in (I) exhibit a small, an expected, and a large Zr—CH2Ph angle. The angles are similar to those of the closely related tribenzyl[η5‐(benzyldimethylsilyl)cyclopentadienyl]zirconium complex. The smallest Zr—CH2Ph angle and the consequently relatively short Zr?Cipso distance are indicative of η2‐bonding of the benzyl group. 相似文献
68.
We consider the linear model Y = Xβ + ε that is obtained by discretizing a system of first-kind integral equations describing a set of physical measurements. The n vector β represents the desired quantities, the m x n matrix X represents the instrument response functions, and the m vector Y contains the measurements actually obtained. These measurements are corrupted by random measuring errors ε drawn from a distribution with zero mean vector and known variance matrix. Solution of first-kind integral equations is an ill-posed problem, so the least squares solution for the above model is a highly unstable function of the measurements, and the classical confidence intervals for the solution are too wide to be useful. The solution can often be stabilized by imposing physically motivated nonnegativity constraints. In a previous article (O'Leary and Rust 1986) we developed a method for computing sets of nonnegatively constrained simultaneous confidence intervals. In this article we briefly review the simultaneous intervals and then show how to compute nonnegativity constrained one-at-a-time confidence intervals. The technique gives valid confidence intervals even for problems with m < n. We demonstrate the methods using both an overdetermined and an underdetermined problem obtained by discretizing an equation of Phillips (Phillips 1962). 相似文献
69.
70.
Sterrer M Fischbach E Heyde M Nilius N Rust HP Risse T Freund HJ 《The journal of physical chemistry. B》2006,110(17):8665-8669
The formation of surface color centers (F(S) centers) by electron bombardment of thin MgO(001) films is investigated using electron paramagnetic resonance and low-temperature scanning tunneling microscopy. At low electron doses both techniques indicate the formation of singly occupied color centers (F(S)(+)), whereas at high electron doses the doubly occupied type (F(S)(0)) is dominant. It is suggested that with increasing electron dose F(S)(+) centers are transformed into F(S)(0). Tunneling spectra of individual F(S)(0) centers reveal a large distribution of energetic positions of occupied and unoccupied states, which is caused by local variations of the coordination number of the defects and explains the broad signals usually detected with integrating spectroscopic techniques. 相似文献