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41.
Valla T Fedorov AV Johnson PD Glans PA McGuinness C Smith KE Andrei EY Berger H 《Physical review letters》2004,92(8):086401
High-resolution photoemission has been used to study the electronic structure of the charge-density wave (CDW) and superconducting dichalcogenide, 2H-NbSe2. From the extracted self-energies, important components of the quasiparticle interactions have been identified. In contrast to previously studied TaSe2, the CDW transition does not affect the electronic properties significantly. The electron-phonon coupling is identified as a dominant contribution to the quasiparticle self-energy and is shown to be very anisotropic (k dependent) and much stronger than in TaSe2. 相似文献
42.
FT-IR spectroscopy and SFM were used to investigate the growth of thin films of the organic semiconductor 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) deposited by vacuum sublimation onto various substrates, i.e. Ag(111) layers on mica, KBr(100), mica, oxidized Si, and TiO2 nanoparticles on Si. Layer thicknesses of PTCDA varied from 10 to 1500 nm.The anhydride vibrations of PTCDA differ for the used substrates, which can be connected to the orientation of the molecules relative to the substrate surface and the film morphology as detected in the SFM pictures. 相似文献
43.
In many magnetic materials, spin dynamics at short times are dominated by precessional motion as damping is relatively small. We describe how avalanches evolve under these conditions. The growth front is spread out over a large region and consists of rapidly fluctuating spins often above the ferromagnetic transition temperature. In the limit of no damping the system will transition to an ergodic state if the initial instability is large enough, but otherwise can die out. This dynamic nucleation phenomenon is analyzed theoretically and the implications for real materials are discussed. 相似文献
44.
Eguchi K Enomoto S Furuno K Goldman J Hanada H Ikeda H Ikeda K Inoue K Ishihara K Itoh W Iwamoto T Kawaguchi T Kawashima T Kinoshita H Kishimoto Y Koga M Koseki Y Maeda T Mitsui T Motoki M Nakajima K Nakajima M Nakajima T Ogawa H Owada K Sakabe T Shimizu I Shirai J Suekane F Suzuki A Tada K Tajima O Takayama T Tamae K Watanabe H Busenitz J Djurcic Z McKinny K Mei DM Piepke A Yakushev E Berger BE Chan YD Decowski MP Dwyer DA Freedman SJ Fu Y Fujikawa BK Heeger KM Lesko KT Luk KB Murayama H 《Physical review letters》2003,90(2):021802
KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded. 相似文献
45.
P. Gasik K. Piasecki N. Herrmann Y. Leifels T. Matulewicz A. Andronic R. Averbeck V. Barret Z. Basrak N. Bastid M. L. Benabderrahmane M. Berger P. Buehler M. Cargnelli R. Čaplar P. Crochet O. Czerwiakowa I. Deppner P. Dupieux M. Dželalija L. Fabbietti Z. Fodor I. Gašparić Y. Grishkin O. N. Hartmann K. D. Hildenbrand B. Hong T. I. Kang J. Kecskemeti Y. J. Kim M. Kirejczyk M. Kiš P. Koczon R. Kotte A. Lebedev A. Le Fèvre J. L. Liu X. Lopez V. Manko J. Marton R. Münzer M. Petrovici F. Rami A. Reischl W. Reisdorf M. S. Ryu P. Schmidt A. Schüttauf Z. Seres B. Sikora K. S. Sim V. Simion K. Siwek-Wilczyńska V. Smolyankin K. Suzuki Z. Tymiński P. Wagner I. Weber E. Widmann K. Wiśniewski Z. G. Xiao I. Yushmanov Y. Zhang A. Zhilin V. Zinyuk J. Zmeskal 《The European Physical Journal A - Hadrons and Nuclei》2016,52(6):177
46.
Trigger efficiencies at BESⅢ were determined for both the J/ψ and ψ' data taking of 2009. Both dedicated runs and physics datasets are used; efficiencies are presented for Bhabha-scattering events, generic hadronic decay events involving charged tracks, dimuon events and ψ'→π+π-J/ψ, J/ψ→ 1+1- events.The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BESⅢ design specifications. 相似文献
47.
Three-dimensional magnetic resonance spectroscopic imaging of histologically confirmed brain tumors 总被引:6,自引:0,他引:6
Vigneron D Bollen A McDermott M Wald L Day M Moyher-Noworolski S Henry R Chang S Berger M Dillon W Nelson S 《Magnetic resonance imaging》2001,19(1):89-101
The goal of this study was to determine whether presurgical metabolite levels measured by 3D MR Spectroscopic Imaging (MRSI) can accurately detect viable cancer within human brain tumor masses. A total of 31 patients (33 exams, 39 pathology correlations) with brain tumors were studied prior to surgical biopsy and/or resection. The 3D MRSI was obtained with a spatial resolution of 0.2 to 1 cc throughout the majority of the mass and adjacent brain tissue using PRESS-CSI localization. Levels of choline, creatine and NAA were estimated from the locations of the resected tissue and normalized to normal appearing brain tissue. The data were correlated with subsequent histologic analysis of the biopsy tissue samples. Although there were large variations in the metabolite ratios, all regions of confirmed cancer demonstrated significant choline levels and a mean choline/NAA ratio of 5.84 + 2.58 with the lowest value being 1.3. This lowest value is greater than 4 standard deviations above the mean (0.52 +/- 0.13) found in 8 normal volunteers. The choline signal intensities in confirmed cancers were significantly elevated compared to normal appearing brain tissue with a mean ratio of 1.71 +/- 0.69. Spectra with no significant metabolite levels were observed in the non-enhancing necrotic core of the tumor masses. The results of this study indicate that 3D MRSI of brain tumors can detect abnormal metabolite levels in regions of viable cancer and grades and can differentiate cancer from necrosis and/or normal brain tissue. 相似文献
48.
S.V. Dordevic D.N. Basov R.C. Dynes B. Ruzicka V. Vescoli L. Degiorgi H. Berger R. Gaál L. Forró E. Bucher 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(1):15-23
We present a comprehensive analysis of the optical constants of the two-dimensional dichalcogenide materials 2
H
-
TaSe
2
and 2
H
-
NbSe
2
, in an attempt to address the physics of two-dimensional correlated systems. The title compounds were studied over several
decades in frequency, from the far-infrared to the ultraviolet. Measurements with linearly polarized light have allowed us
to obtain both the in-plane and out-of-plane components of the conductivity tensor. Although the electromagnetic response
of dichalcogenides is strongly anisotropic, both the in-plane and out-of-plane components of the conductivity tensor share
many common features, including the presence of a well-defined metallic component, as well as a “mid-infrared band”. We discuss
the implications of these results in the context of the spectroscopic results of other classes of low-dimensional conductors
such as the high-temperature superconducting cuprates. In particular, the analysis of the redistribution of the spectral weight
as a function of temperature, as well as the behavior of the quasiparticles relaxation rate, points to significant distinctions
between the charge dynamics of dichalcogenides and other classes of low dimensional conductors.
Received 28 October 2002 / Received in final form 10 March 2003 Published online 23 May 2003
RID="a"
ID="a"e-mail: degiorgi@solid.phys.ethz.ch 相似文献
49.
L. Despont F. Clerc M. G. Garnier H. Berger L. Forró P. Aebi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(3):421-426
Multiple scattering theory based on a
cluster model is used to simulate full hemispherical X-ray photoelectron
diffraction measurements on a 1T-TaS2(0001) surface. Key points to determine the surface termination are discussed. As the commonly applied single scattering simulations
do not give satisfying results, a multiple scattering approach has to be used to accurately simulate the full hemispherical
photoelectron diffraction patterns. Differences and similarities between calculations of Ta and S terminated surfaces are
presented along with experimental results at room temperature using both, the single and the multiple scattering approaches.
We find that the surface is S terminated and that the quantitative difference between the calculations for both terminations
permits to show the limits of the single scattering approach for solving surface termination problems. Moreover, by generalizing
the results obtained using the multiple scattering approach, we discuss the application of this method to other similar systems. 相似文献
50.
Berger EL Harris BW Kaplan DE Sullivan Z Tait TM Wagner CE 《Physical review letters》2001,86(19):4231-4234
A long-standing discrepancy between the bottom-quark production cross section and predictions of perturbative quantum chromodynamics is addressed. We show that pair production of light gluinos, of mass 12 to 16 GeV, with two-body decays into bottom quarks and light bottom squarks, yields a bottom-quark production rate in agreement with hadron collider data. We examine constraints on this scenario from low-energy data and make predictions that may be tested at the next run of the Fermilab Tevatron collider. 相似文献