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71.
Batani D Baton SD Manclossi M Santos JJ Amiranoff F Koenig M Martinolli E Antonicci A Rousseaux C Le Gloahec MR Hall T Malka V Cowan TE King J Freeman RR Key M Stephens R 《Physical review letters》2005,94(5):055004
We study the propagation of fast electrons in a gas at different densities. A large relativistic electron current is produced by focusing a short-pulse ultrahigh-intensity laser on a metallic target. It then propagates in a gas jet placed behind the foil. Shadowgraphy in the gas shows an electron cloud moving at sub-relativistic average velocities. The experiment shows (i) the essential role of the density of background material for allowing propagation of fast electrons, (ii) the importance of the ionization phase which produces free electrons available for the return current, and (iii) the effect of electrostatic fields on fast-electron propagation. 相似文献
72.
Snavely RA Key MH Hatchett SP Cowan TE Roth M Phillips TW Stoyer MA Henry EA Sangster TC Singh MS Wilks SC MacKinnon A Offenberger A Pennington DM Yasuike K Langdon AB Lasinski BF Johnson J Perry MD Campbell EM 《Physical review letters》2000,85(14):2945-2948
An intense collimated beam of high-energy protons is emitted normal to the rear surface of thin solid targets irradiated at 1 PW power and peak intensity 3x10(20) W cm(-2). Up to 48 J ( 12%) of the laser energy is transferred to 2x10(13) protons of energy >10 MeV. The energy spectrum exhibits a sharp high-energy cutoff as high as 58 MeV on the axis of the beam which decreases in energy with increasing off axis angle. Proton induced nuclear processes have been observed and used to characterize the beam. 相似文献
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75.
Examining the possibility that the enhancement of Tc in the tungsten bronzes arises from interband coupling, we find that a single density of states provides reasonable quantitative agreement with the Tc enhancement, the heat capacity and the magnetic susceptibility. 相似文献
76.
Three new Fe-defect complexes have been identified by ESR in Fe doped crystals of SrTiO3. These are an Fe3+ center with rhombic fine structure in the “as-grown” crystals, and the vacancy associated complexes Fe2+ -Vo and Fe1+ -Vo in “reduced” crystals. Photo-excited charge transfer effects are observed for these centers. 相似文献
77.
We investigate the direct effects of phonon softening on Tc in Nb3Sn. It is inadequate to explain the high Tc, which arises instead from an unusually large electron- phonon coupling to the two Γ'12 optical phonon modes. 相似文献
78.
J. Amirzadeh R.E. Ansorge M. Baubillier I.J. Bloodworth G.J. Bossen A. Burns J.N. Carney J.R. Carter C.A. Cowan G.F. Cox U. Dore Ph. Gavillet J.K. Hassall J.B. Kinson K. Knudson F. Levy P.F. Loverre R. Zitoun 《Physics letters. [Part B]》1979,89(1):125-130
We present evidence for a narrow Y1 with a mass of 3.17 GeV and a width ? 20 MeV decaying to ΣKK? + pions, ΛKK? + pions and ΞK + pions. The data come from two high statistics K?p bubble chamber experiments with a sensitivity of ≈100 eV/μbat 8.25 GeV/c and ≈ 45 eV/μbat 6.5 GeV/c. 相似文献
79.
A mechanism is proposed to explain the double phase transitions found in K2PbCu(NO2)6 and Tl2PbCu(NO2)6. The higher temperature transition is caused by the cooperative Jahn-Teller effect. The lower temperature transition occurs as the fourth order anharmonic interaction restabilizes the lattice against instabilities caused by static distortions in the third order anharmonic interaction. Calculated curves of the order parameter and heat capacity reproduce all the features in the experimental curves. 相似文献
80.
Vicic DA Anderson TJ Cowan JA Schultz AJ 《Journal of the American Chemical Society》2004,126(26):8132-8133
Reaction of two equiv of 1-adamantylzinc bromide with (dippm)NiBr2 (dippm = bis(di-isopropylphosphino)methane) led to a dinuclear metal complex containing a unique linear bridging hydride ligand. The hydride was characterized by neutron diffraction methods, which confirmed a linear bonding mode. Preliminary reactivity studies of this unusual dimer are reported. 相似文献