排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
The systems AeAl(2-x)Mgx (Ae = Ca, Sr, Ba) display electron concentration induced Laves phase structural changes. However, the complete sequence MgCu2 --> MgNi2 --> MgZn2 with increasing x (decreasing electron count) is only observed for Ae = Ca. Compounds SrAl(2-x)Mgx (0 < x < or = 2) and BaAl(2-x)Mgx (x = 0.85 and 2.0) were synthesized and structurally characterized by X-ray diffraction experiments. For the Sr system the structural sequence CeCu2 --> MgNi2 --> MgZn2 occurs with increasing Mg content x. Thus, larger Sr does not allow the realization of the MgCu2 structure at low x. For Ae = Ba a binary compound BaAl2 does not exist, but more Ba-rich Ba7Al13 forms. The reinvestigation of the crystal structure of Ba7Al13 by selected area and convergent beam electron diffraction in a transmission electron microscope revealed a superstructure, which subsequently could be refined from single X-ray diffraction data. The formula unit of the superstructure is Ba21Al40 (space group P31m, Z = 1, a = 10.568(1) angstroms, c = 17.205(6) angstroms). In Ba21Al40 a size match problem between Ba and Al present in Ba7Al13 is resolved. The structure of Ba7Al13 (Ba21Al40) can be considered as a Ba excess variant of the hexagonal MgNi2 Laves phase type structure. An incommensurately modulated variant of the MgNi2 structure is obtained for phases BaAl(2-x)Mgx with x = 0.8-1. At even higher Mg concentrations a structural change to the proper MgZn2 type structure takes place. 相似文献
2.
3.
Akchurin N Langland J Onel Y Bonner BE Corcoran MD Cranshaw J Nessi-Tedaldi F Nessi M Nguyen C Roberts JB Skeens J White JL Bravar A Giacomich R Penzo A Schiavon P Zanetti A Bystricky J Lehar F de Lesquen A van Rossum L Cossairt JD Read AL Derevschikov AA Matulenko YA Meschanin AP Nurushev SB Patalakha DI Rykov VL Solovyanov VL Vasiliev AN Grosnick DP Hill DA Laghai M Lopiano D Ohashi Y Shima T Spinka H Stanek RW Underwood DG Yokosawa A Funahashi H Goto Y Imai K Itow Y Makino S Masaike A 《Physical review D: Particles and fields》1993,48(7):3026-3036
4.
Ditzler WR Hill D Hoftiezer J Johnson KF Lopiano D Shima T Shimizu H Spinka H Stanek R Underwood D Wagner RG Yokosawa A Burleson GR Faucett JA Fontenla CA Garnett RW Luchini C Rawool-Sullivan MW Bhatia TS Glass G Hiebert JC Kenefick RA Nath S Northcliffe LC Damjanovich R Jarmer JJ Vaninetti J Jeppesen RH Tripard GE 《Physical review D: Particles and fields》1992,46(7):2792-2830
5.
We have analyzed data on K+p elastic scattering at 21 momenta covering the range 0.5–2.5 GeV/c. We present results of three phase shift analyses. One of these is an energy independent accelerated convergence expansion (ACE) analysis in which high partial waves are included through use of conformal mapping as suggested by analytic approximation theory. The other two are an energy independent and an energy smoothed conventional analysis. The ACE method gave, with the same number of parameters, a 20% average improvement in x2 as well as more unique phase shift solutions. The high partial waves gave significant contributions to total and inelastic cross sections. The ACE method is also sensitive to the value of gΛΣ2 = gKΛN2 + gKΣN2; we have obtained the value gΛΣ2 = 15.2 ± 2.3. 相似文献
6.
7.
8.
Striking regularities are observed in πN backward elastic scattering for plab ? 1 GeV. The rich structure of the polarization and differential cross section vary rapidly in both angle and energy. For a fixed energy however, the observables approximately satisfy the derivative relation . This empirical relation is shown to be the consequence of the peripheral nature of the interaction at high energies and the dominance of successive partial waves with increasing energy W = √s at lower energies: l = 2,3,4 … for W = 1.68, 1.95, 2.18 … GeV, respectively. suggests a pattern where N,Δ and Δ,Δ states appear in nearly degenerate pairs with the same l and parity but with . The observed regularities are consistent with measurements in the inelastic channel π?p → ΛK0 and could provide a useful tool for an extension of phase-shift analyses to higher energies where no prominent peaks in the total cross section constrain the solution. At the highest energy (plab = 6 GeV/c) a possible deviation from the derivative rule implies the onset of a non-peripheral contribution not present at lower energies. 相似文献
9.
Akihiko Yokosawa 《Physics Reports》1980,64(2):49-86
Some experimental results from the polarized-beam program at the Argonne ZGS are reviewed. The main emphasis is placed on the elastic-scattering and total cross-section measurements. 相似文献
10.