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71.
72.
MR Eskildsen AB Abrahamsen PL Gammel DJ Bishop NH Andersen K Mortensen PC Canfield 《Pramana》2002,58(5-6):903-905
We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor
LuNi2B2C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above
10 K the transition onset field. H
2(T), rises sharply, bending away from H
c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H
tr=3–3.5 kOe. Below H
tr the FLL nearest neighbor direction is parallel to the b-axis, and above H
tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model. 相似文献
73.
SCF Xα calculations are reported for a cyclic molecule whose bonding sequence is a model for the backbone bonding sequence in the polydiacetylenes. The electronic structure of the model molecule, with particular emphasis on the two lowest energy optical transitions, is determined in conjunction with a systematic variation in bonding sequence. Transition energies are in fair agreement with experiment for polydiacetylenes with the acetylene linkage, , and for the model molecule in solution. The same analysis predicts a substantial red shift on going to the butatriene linkage, , whereas a small blue-shift is observed experimentally. This qualitative disagreement between theory and experiment is attributed to the inability of the present scheme to represent excitonic excitations and/or the neglect of interchain interactions. The transition energies from the SCF Xα treatment can be satisfactorily represented in a simple Hückel model with the following resonance integral-bond length relationship:βij = 67.28 exp (-dij/0.424) eV. 相似文献
74.
K. V. Chance W. A. Traub K. W. Jucks D. G. Johnson 《International Journal of Infrared and Millimeter Waves》1991,12(6):581-588
The magnetic dipole-allowed spin-rotation lines of O2 potentially can be used for pointing calibration and confirmation of float altitude for far infrared spectra of the stratosphere obtained from balloon platforms. We demonstrate that current deficiencies in the spectroscopic database, particularly the air pressure-broadening coefficients, severely limit the capability of deriving useful pointing calibrations, and that precise pressure-broadening measurements for the transitions actually used in calibration are needed to improve this capability. 相似文献
75.
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77.
A new method for characterizing living tissue cells is demonstrated using both phase and amplitude information derived from the spectrally resolved interferogram in a single measurement.The effect of the light source spectral distribution can be cancelled out with the help of the zero order spectrum of the Fourier transform of the interferogram.The ratio of amplitudes between the two interference beams is acquired without this effect.The group delay,the first and second order dispersions,and the absorption,etc.,for the full wavelength range can be measured.The results of the culture medium and the HeLa living cells are given.In addition,the measured values of d2 n/dλ2 and absorption of the distilled water are also provided for comparison. 相似文献
78.
79.
Panitkin SY Ajitanand NN Alexander J Anderson M Best D Brady FP Case T Caskey W Cebra D Chance J Chung P Cole B Crowe K Das A Draper J Gilkes M Gushue S Heffner M Hirsch A Hjort E Huo L Justice M Kaplan M Keane D Kintner J Klay J Krofcheck D Lacey R Lauret J Lisa MA Liu H Liu YM McGrath R Milosevich Z Odyniec G Olson D Pinkenburg C Porile N Rai G Ritter HG Romero J Scharenberg R Schroeder LS Srivastava B Stone NT Symons TJ Wang S Wells R Whitfield J Wienold T Witt R Wood L Yang X Zhang WN 《Physical review letters》2001,87(11):112304
We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis. 相似文献
80.
Chung P Ajitanand NN Alexander JM Anderson M Best D Brady FP Case T Caskey W Cebra D Chance JL Cole B Crowe K Das A Draper JE Gilkes ML Gushue S Heffner M Hirsch AS Hjort EL Huo L Justice M Kaplan M Keane D Kintner JC Klay J Krofcheck D 《Physical review letters》2000,85(5):940-943
We have measured the sideward flow of neutral strange ( K(0)(s)) mesons in 6A GeV Au+Au collisions. A prominent antiflow signal is observed for an impact parameter range ( b less, similar7 fm) which spans central and midcentral events. Since the K(0)(s) scattering cross section is relatively small in nuclear matter, this observation suggests that the in-medium kaon vector potential plays an important role in high density nuclear matter. 相似文献