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71.
Wong KL Chu MS Luce TC Petty CC Politzer PA Prater R Chen L Harvey RW Austin ME Johnson LC La Haye RJ Snider RT 《Physical review letters》2000,85(5):996-999
Experimental evidence is reported of an internal kink instability driven by a new mechanism: barely trapped suprathermal electrons produced by off-axis electron cyclotron heating on the DIII-D tokamak. It occurs in plasmas with an evolving safety factor profile q(r) when q(min) approaches 1. This instability is most active when ECCD is applied on the high field side of the flux surface. It has a bursting behavior with poloidal/toroidal mode number = m/n = 1/1. In positive magnetic shear plasmas, this mode becomes the fishbone instability. This observation can be qualitatively explained by the drift reversal of the barely trapped suprathermal electrons. 相似文献
72.
LeClair P Swagten HJ Kohlhepp JT van De Veerdonk RJ de Jonge WJ 《Physical review letters》2000,84(13):2933-2936
Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small. 相似文献
73.
We present results on the dependence of the initial luminescence decay in hydrogenated amorphous Si on temperature, excitation photon energy and excitation intensity. We find that the initial decay becomes faster with increasing temperature and excitation intensity but slower with increasing excitation phonon energy. The total luminescence intensity varies sublinearly with excitation intensity at high intensities, showing that nonradiative processes become more important at high intensities. These results are discussed in terms of current models. 相似文献
74.
The solution phase combinatorial Bohlmann-Rahtz reaction gives highly functionalized pyridine libraries from enamino esters and alkynones in a single synthetic step. Good product ratios and library purities were obtained in reactions catalyzed by zinc(II) bromide, the acid-catalyzed heteroannulation procedure offering considerable improvements over traditional methodology. 相似文献
75.
J. H. Bagley 《Stochastic Processes and their Applications》1985,20(2):333-341
If Z (t) is the sum of the characteristics at time t of the population in a Crump-Mode-Jagers branching process, and T is the time to extinction, it is known that under certain conditions, the distribution of Z (t) conditioned on {T > t} converges to a proper distribution as t→∞. We derive necessary and sufficient conditions in terms of the offspring process, for the existence of integral moments of this limit distribution. 相似文献
76.
We report large shifts in the photoluminescence spectrum of a-Si:H as the excitation energy is reduced below ~1.8 eV. The shifts in the position of maxima are equal to approximately half the change in excitation energy. Another interesting feature of the data is a sharp high energy cutoff of the spectrum, also at ~1.8 eV, when excited above that energy. 相似文献
77.
Le Roy RJ 《Journal of Molecular Spectroscopy》1999,194(2):189-196
A new way of representing vibration-rotation term values for multiple isotopomers of a given electronic state of a diatomic molecule is presented which resolves problems associated with the way the conventional combined isotopomer expansion represents the atomic mass-dependent JWKB and Born-Oppenheimer breakdown correction terms. Its application to infrared and microwave data for HF and DF yields new Dunham expansion coefficients and Born-Oppenheimer breakdown correction terms for this species. This procedure is implemented in a generally available computer program for fitting to various types of data involving one or several electronic states of multiple isotopomers of a diatomic molecule. Copyright 1999 Academic Press. 相似文献
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