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91.
Cinchetti M Sánchez Albaneda M Hoffmann D Roth T Wüstenberg JP Krauss M Andreyev O Schneider HC Bauer M Aeschlimann M 《Physical review letters》2006,97(17):177201
The femtosecond magnetization dynamics of a thin cobalt film excited with ultrashort laser pulses has been studied using two complementary pump-probe techniques, namely, spin-, energy-, and time-resolved photoemission and the time-resolved magneto-optical Kerr effect. Combining the two methods, it is possible to identify the microscopic electron spin-flip mechanisms responsible for the ultrafast macroscopic magnetization dynamics of the cobalt film. In particular, we show that electron-magnon excitation does not affect the overall magnetization even though it is an efficient spin-flip channel on the sub-200 fs time scale. Instead, we find experimental evidence for the relevance of Elliott-Yafet-type spin-flip processes for the ultrafast demagnetization taking place on a time scale of 300 fs. 相似文献
92.
Rueff JP Itié JP Taguchi M Hague CF Mariot JM Delaunay R Kappler JP Jaouen N 《Physical review letters》2006,96(23):237403
We report on the most complete investigation to date of the -electron properties at the transition in elemental Ce by resonant inelastic x-ray scattering (RIXS). The Ce 2p3d-RIXS spectra were measured directly in the bulk material as a function of pressure through the transition. The spectra were simulated within the Anderson impurity model. The occupation number n(f) and f double occupancy were derived from the calculations in both gamma and alpha phases in the ground state. We find that the electronic structure changes result mainly from band formation of 4f electrons which concurs with reduced electron correlation and increased Kondo screening at high pressure. 相似文献
93.
Herranz G Ranchal R Bibes M Jaffrès H Jacquet E Maurice JL Bouzehouane K Wyczisk F Tafra E Basletic M Hamzic A Colliex C Contour JP Barthélémy A Fert A 《Physical review letters》2006,96(2):027207
We report on tunneling magnetoresistance (TMR) experiments that demonstrate the existence of a significant spin polarization in Co-doped (La, Sr)TiO(3-delta) (Co-LSTO), a ferromagnetic diluted magnetic oxide system (DMOS) with high Curie temperature. These TMR experiments have been performed on magnetic tunnel junctions associating Co-LSTO and Co electrodes. Extensive structural analysis of Co-LSTO combining high-resolution transmission electron microscopy and Auger electron spectroscopy excluded the presence of Co clusters in the Co-LSTO layer and thus, the measured ferromagnetism and high spin polarization are intrinsic properties of this DMOS. Our results argue for the DMOS approach with complex oxide materials in spintronics. 相似文献
94.
Aniol KA Armstrong DS Averett T Benaoum H Bertin PY Burtin E Cahoon J Cates GD Chang CC Chao YC Chen JP Choi S Chudakov E Craver B Cusanno F Decowski P Deepa D Ferdi C Feuerbach RJ Finn JM Frullani S Fuoti K Garibaldi F Gilman R Glamazdin A Gorbenko V Grames JM Hansknecht J Higinbotham DW Holmes R Holmstrom T Humensky TB Ibrahim H de Jager CW Jiang X Kaufman LJ Kelleher A Kolarkar A Kowalski S Kumar KS Lambert D LaViolette P LeRose J Lhuillier D Liyanage N Margaziotis DJ Mazouz M McCormick K 《Physical review letters》2006,96(2):022003
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero. 相似文献
95.
In this contribution, we study several monocarbonyl-metal complexes in order to unravel the contribution of relativistic effects to the metal-ligand bond length and complexation energy. Using scalar density functional theory (DFT) constrained space orbital variation (CSOV) energy decomposition analysis supplemented by all-electron four-component DFT computations, we describe the dependency of relativistic effects on the orbitals involved in the complexation for the Au(+) isoelectronic series, namely, the fully occupied 5d orbitals and the empty 6s orbitals. We retrieve the well-known sensitivity of gold toward relativity. For platinum and gold, the four-component results illustrate the simultaneous relativistic expansion of the 5d orbitals and the contraction of the 6s orbitals. The consequences of such modifications are evidenced by CSOV computations, which show the importance of both donation and backdonation within such complexes. This peculiar synergy fades away with mercury and thallium for which coordination becomes driven by the accepting 6s orbitals only, which makes the corresponding complexes less sensitive toward the relativistic effects. 相似文献
96.
The zeroth order excitonic wave-function built previously is considered as a zeroth order wave-function for the excited state. The interaction with other singly, doubly and triply excited determinants is taken into account through a 2nd order perturbation process. A proper definition of the unperturbed Hamiltonian allows cancellation between the ground state and excited state series, and thus the direct calculation of transition energies. The complete localization of MO's in the CNDO approximation makes the calculation very rapid. The method is applied to the series of linear polyenes H-(CH=CH)
N
-H(2N7) with the CNDO/2 parametrization. The evolution of the excitonic wave-function is analyzed.
Zusammenfassung Die zuvor konstruierte excitonische Wellenfunktion nullter Ordnung wird als Wellenfunktion nullter Ordnung für den angeregten Zustand verwendet. Die Wechselwirkung mit anderen einfach, doppelt und dreifach angeregten Determinanten wird mittels Störungsrechnung 2. Ordnung berücksichtigt. Bei geeigneter Wahl des ungestörten Hamiltonoperators hebt sich der Grundzustand bei Berechnung der Übergangsenergien heraus, was auf ihre direkte Bestimmung hinausläuft. Die vollständige Lokalisierung der MO's hat zur Folge, daß bei Anwendung des CNDO-Verfahrens die Berechnung sehr schnell vonstatten geht. Die Methode wird auf die Reihe linearer Polyene des Typs H-(CH=CH) N -H(2N7) angewendet (CNDO/2-Parametrisierung). Die excitonische Wellenfunktion wird bezüglich der Zellenpopulation und deren Schwankungen untersucht.
Résumé On prend la fonction d'onde excitonique déjà construite comme fonction d'onde d'ordre zéro pour l'état excité. L'interaction avec les autres déterminants monoexcités, les déterminants diet tri-excités est prise en considération par une perturbation au 2è ordre. Un choix judicieux de l'Hamiltonien non perturbé met en évidence d'importantes suppressions entre les séries de l'état excité et de l'état fondamental, et par conséquent le calcul direct des énergies de transition. Malgré le caractère multiconfigurationel de 0, la localization complete des OM rend le calcul extrêmement rapide dans les hypothèses CNDO. La méthode est appliquée à la série des polyènes linéaires H-(CH=CH) N -H (N = 2 à 7). Analyse de la fonction d'onde excitonique en terme de populations de loge et de leur fluctuations.相似文献
97.
Mackle JN Blond DJ Mooney E McDonnell C Blau WJ Shaw G Barry FP Murphy JM Barron V 《Macromolecular bioscience》2011,11(9):1272-1282
In an effort to reduce organ replacement and enhance tissue repair, there has been a tremendous effort to create biomechanically optimized scaffolds for tissue engineering applications. In contrast, the development and characterization of electroactive scaffolds has attracted little attention. Consequently, the creation and characterization of a carbon nanotube based poly(lactic acid) nanofiber scaffold is described herein. After 28 d in physiological solution at 37 °C, a change in the mass, chemical properties and polymer morphology is seen, while the mechanical properties and physical integrity are unaltered. No adverse cytotoxic affects are seen when mesenchymal stem cells are cultured in the presence of the scaffold. Taken together, these data auger well for electroactive tissue engineering.
98.
Olsson FE Persson M Borisov AG Gauyacq JP Lagoute J Fölsch S 《Physical review letters》2004,93(20):206803
The Cu adatom-induced localization of the two-dimensional Shockley surface state at the Cu(111) surface was identified from experimental and simulated scanning tunneling microscopy spectra. The localization gives rise to a resonance located just below the surface state band edge. The adatom-induced surface state localization is discussed in terms of the existence theorem for bound states in any attractive two-dimensional potential. We also identify adatom-induced resonance states deriving from atomic orbitals in both experimental and simulated spectra. 相似文献
99.
The 1H and 13C NMR resonances of 15 N,N'-diacylproflavines were assigned completely and unequivocally using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC). 相似文献
100.
Gross P Klein ME Ridderbusch H Lee DH Meyn JP Wallenstein R Boller KJ 《Optics letters》2002,27(16):1433-1435
We present a novel technique for tuning an optical parametric oscillator (OPO) through electro-optically induced shape variations of the parametric gain spectrum in quasi-phase-matched lithium niobate (LN). The diode-pumped, triply resonant continuous-wave OPO is based on a 58-mm-long LN crystal that consists of three equally long sections, the outer sections being periodically poled with a 50% duty cycle. The center section is single-domain material and serves as a tunable phase shifter through the electro-optic effect. By application of a voltage of up to 1230 V, the OPO signal and idler wavelengths are tuned over 102 nm from 1560 to 1660 nm, in good agreement with theory. 相似文献