共查询到20条相似文献,搜索用时 15 毫秒
1.
H. van Pee O. Bartholomy V. Crede A. V. Anisovich G. Anton R. Bantes Yu. Beloglazov R. Bogendörfer R. Castelijns A. Ehmanns J. Ernst I. Fabry H. Flemming A. Fösel M. Fuchs Ch. Funke R. Gothe A. Gridnev E. Gutz St. Höffgen I. Horn J. Hößl J. Junkersfeld H. Kalinowsky F. Klein E. Klempt H. Koch M. Konrad B. Kopf B. Krusche J. Langheinrich H. Löhner I. Lopatin J. Lotz H. Matthäy D. Menze J. Messchendorp V. A. Nikonov D. Novinski M. Ostrick A. Radkov A. V. Sarantsev S. Schadmand C. Schmidt H. Schmieden B. Schoch G. Suft V. Sumachev T. Szczepanek U. Thoma D. Walther Ch. Weinheimer 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):61-77
Photoproduction of π0-mesons was studied with the Crystal-Barrel detector at ELSA for incident energies from 300MeV to 3GeV. Differential cross-sections
dσ/dΩ, dσ/dt, and the total cross-section are presented. For E
γ < 3GeV, the angular distributions agree well with the SAID parametrization. At photon energies above 1.5GeV, a strong forward
peaking indicates t-channel exchange to be the dominant process. The rapid variations of the cross-section with energy and angle indicate production
of resonances. An interpretation of the data within the Bonn-Gatchina partial-wave analysis is briefly discussed. 相似文献
2.
V. Berardi M. Armenante R. Bruzzese F. Esposito S. Solimeno N. Spinelli S. Bakhramov 《Il Nuovo Cimento D》1991,13(4):423-433
The intensity dependence of the multiphoton ionization spectra of Xe atoms has been investigated with an improved accuracy
and well-controlled laser parameters. In particular, we have examined the ionization rates for X3+, X2−, X+ as functions of the laser intensity and the pressure in the target chamber. The apparatus used for these measurements is
characterized by a high-energy resolution (better than 200 meV) and a completely digital acquisition system. The time-of-flight
spectra clearly show the contributions of the different isotopes present in Xe gas. The laser pulses have been characterized
with great accuracy by monitoring the energy, pulse width and divergence shot by shot. The ionization rates of the different
ions have been used for testing the basic assumption of the Geltman theory of multiple ionization based on the single electron
ionization model. We have found that for the small intensity range investigated the quantity (dXe
+/dI)·(dXe
3+/dI)/(dXe
2+/dI)2 appears to be quite close to the value 0.5 predicted by this model. 相似文献
3.
V. V. Balashov V. K. Dolinov 《The European Physical Journal A - Hadrons and Nuclei》2008,37(1):97-110
An extended set of observables of the nuclear quasi-free (p, dπ+) reaction including the triple differential cross-section for coincidence measurements, its analyzing power in case of polarized
proton beams and, also, the parameters of the polarization of the excited recoil nucleus and the produced deuteron are considered
in the framework of the distorted-wave impulse approximation using the reaction 16O(p, dπ+)15N at a proton energy of 650 MeV as an example. The calculations show a high sensitivity of the differential cross-section
and, especially, of the polarization transfer characteristics of the reaction to the spin-multipole decomposition of the amplitude
of the basic two-body pp → dπ+ process. 相似文献
4.
R. Citro M. Marinaro 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):235-242
The spin magnetic susceptibility of the p-d model is calculated by means of a perturbation theory in the hybridization term V through a generalized cumulant expansion (GCE). The analysis is approached from the paramagnetic metallic phase. The results
qualitatively reproduce some unusual magnetic properties in the normal state of the hole-doped cuprates, supporting the scenario
of a Van Hove singularity near the Fermi level.
Received 15 October 1998 and Received in final form 24 March 1999 相似文献
5.
C. Merino C. Pajares Yu. M. Shabelski 《The European Physical Journal C - Particles and Fields》2009,59(3):691-703
In the framework of the quark–gluon string model we calculate the inclusive spectra of secondaries produced in d+Au collisions at intermediate (CERN SPS) and at much higher (RHIC) energies. The results of numerical calculations at intermediate
energies are in reasonable agreement with the data. At RHIC energies numerically large inelastic screening corrections (percolation
effects) should be accounted for in the calculations. We extract these effects from the existing experimental data of RHIC
on minimum-bias and central d+Au collisions. The predictions for p+Au interactions at LHC energy are also given. 相似文献
6.
R. Gheisari 《Molecular physics》2013,111(16):1685-1688
The low-energy elastic cross-section in collisions of a muonic atom with the hydrogen isotope is investigated, employing a new wave function (trial) and using the coordinate-space Faddeev–Hahn model. The wave function includes non-adiabatic terms. Our results of s–wave cross-sections are given, at the tμ(1s) + d scattering. Calculated cross-sections are in good accord with the results published by Chiccoli et al., while having no good agreement with other recent reports. 相似文献
7.
G. P. Gupta A. Z. Msezane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):157-160
Excitation energies from ground state for 97 fine-structure levels as well as oscillator strengths and radiative decay rates
for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to
the (1s
22s
22p
6)3s
23p, 3s
3
p
2, 3s
23d, 3p
3, 3s3p3d, 3p
23d, 3s3d
2, 3s
24s, 3s
24p, 3s
24d, 3s
24f, and 3s3p4s configurations of Co XV are calculated, using extensive configuration-interaction (CI) wave functions, obtained with the
CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli
approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal
elements of the Hamiltonian matrices have been made. Our calculated excitation energies, including their ordering, are in
excellent agreement with the experimental results and the experimentally compiled energy values of the National Institute
for Standards and Technology (NIST) wherever available. The mixing among several fine-structure levels is found to be very
strong, with most of the strongly mixed levels belonging to the (1s
22s
22p
6)3p
23d and 3s3d
2 configurations. The strong mixing among several fine-structure levels makes it very difficult to identify them uniquely.
Perhaps, that may be the reason for the lack of both experimental and theoretical results for these levels. We believe that
our extensive calculated values can guide experimentalists in identifying the fine-structure levels in their future work.
From our radiative decay rates we have also calculated radiative lifetimes of some fine-structure levels. In this calculation
we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available. 相似文献
8.
The perfect-nesting instability towards antiferromagnetism of the Hubbard model is suppressed by next-nearest neighbor hopping t′. The asymptotic behavior of the critical coupling Uc(t′) at small t′ is calculated in dimensions d = 2,3, ∞ using Hartree theory; this yields the exact result at least in d > 2. The order of the transition is also determined. A region of stability of a metallic antiferromagnetic phase in d = 3 is identified. 相似文献
9.
We report on the measurements of D
0 and D
s
meson production in 200 GeV Cu+Cu collisions at the STAR at RHIC experiment. Results are discussed with reference to pQCD
predictions of the open charm cross-section as well as the statistical hadronization model. 相似文献
10.
D. Andreasi S. Quaglioni V. D. Efros W. Leidemann G. Orlandini 《The European Physical Journal A - Hadrons and Nuclei》2006,27(1):47-52
The two-body knock-out reaction 4He(e, e'd )d is calculated at various momentum transfers. The full four-nucleon dynamics is taken into account microscopically both in
the initial and the final states. As NN interaction the central MT-I/III potential is used. The calculation shows a strong
reduction of the coincidence cross-section due to the final-state interaction. Nonetheless, the theoretical results exhibit
a considerable overestimation of the experimental cross-section at lower momentum transfer. Comparisons with other, less complete,
calculations suggest that consideration of a more realistic ground state might not be sufficient for a good agreement with
experiment, rather a more realistic final-state interaction could play an essential role. 相似文献
11.
We have measured the gettering efficiencies for Cr, Mn, Fe, Co, Ni and Cu in p/p+ epitaxial wafers. The gettering test started with a reproducible spin-on contamination on the front side of the wafers in
the 1012–1014 atoms/cm2 range, followed by thermal treatment to redistribute the metallic impurities in the wafer. The gettering efficiencies were
measured by a novel wet chemical stratigraphic etching technique in combination with inductively-coupled plasma mass spectrometry.
The residual bulk metal contamination was also measured by this method. This procedure led to global distributions of the
3d elements on the wafer’s front side, in the bulk of the wafer and on the wafer’s back side. Recovery rates were found to be
34%, 2.3%, 100%, 85%, 100% and 100% for Cr, Mn, Fe, Co, Ni and Cu, respectively. An impurity segregation effect in the wafer
bulk was measured for Cu (100%) and Cr (34%), while no detectable segregation-induced gettering mechanisms were detected for
the other elements in the applied concentration range. The segregation-induced gettering mechanisms were interpreted from
the electronic structure of the metallic impurities. For segregation gettering by increased solubility in p+ silicon, the metallic species must form donors. Only Cu+ (3d
10) and Cr+ (3d
5) can form singly positively charged species that exhibit a spherical electronic distribution. It is well known from spinell
structures that 3d
10 and, to a smaller extent 3d
5, are stable configurations in tetrahedral structures like the silicon lattice. Thus, we link the segregation-induced gettering
mechanism in p/p+ epitaxial wafer to the electronic configuration of the 3d elements.
Received: 19 January 2001 / Accepted: 31 January 2001 / Published online: 20 June 2001 相似文献
12.
13.
T. Maitra H. Beck A. Taraphder 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):527-533
The competition between antiferromagnetism and the d + id superconducting state is studied in a model with near and next near neighbour interactions in the absence of any on-site
repulsion. A mean field study shows that it is possible to have simultaneous occurrence of an antiferromagnetic and a singlet
d + id superconducting state in this model. In addition, such a coexistence generates a triplet d + id superconducting order parameter with centre of mass momentum Q = (π,π) dynamically having the same orbital symmetry as the singlet superconductor. Inclusion of next nearest neighbour hopping in the band stabilises
the dxy superconducting state away from half filling, the topology of the phase diagram, though, remains similar to the near neighbour
model. In view of the very recent observation of a broad region of coexistence of antiferromagnetic and unconventional superconducting
states in organic superconductors, the possibility of observation of the triplet state has been outlined.
Received 30 November 2000 and Received in final form 27 March 2001 相似文献
14.
15.
We studied the chemical state of semiconducting and metallic SmS thin films by X-ray photoelectron spectroscopy (XPS), which were fabricated using dual-target magnetron sputtering by controlling the power applied to both metal and chalcogenide targets. On the basis of the valence band spectra obtained, it was suggested that semiconducting SmS has the final state corresponding to the Sm2+(4f6) configuration below the Fermi level, and metallic SmS has mainly the Sm3+(4f5) final state and a virtual band state in the Sm 5d band, contributing to the delocalization of 4f electrons and the emergence of metallic conductivity (4f6d0-4f5d1). Thus, the spectra of our fabricated SmS thin films correspond to the band structure obtained from the dielectric property. This is the first work performed on the intrinsically prepared metallic SmS while the former works done for the sample transformed from semiconductor to metal phase by hard polishing. 相似文献
16.
Zhenlian An Min Zhao Junlan Yao Yewen Zhang Zhongfu Xia 《Applied Physics A: Materials Science & Processing》2009,95(3):801-806
To improve the thermal stability of piezoelectricity of polypropylene (PP) ferroelectrets, chemical modification of the cellular
PP film was performed via chromic acid oxidation and then hydrofluoric acid treatment. Deep chemical modification is achieved
as indicated by the energy-dispersive X-ray analyses on the cross-section of the modified cellular PP film. The results of
the isothermal decay for piezoelectric d
33-coefficient at 70°C indicate the improved thermal stability of piezoelectricity and the enhanced piezoelectric activity of
the modified PP ferroelectrets. The former is attributed to the improvement of thermal stability of the charges trapped in
the internal void surface layers as indicated by the thermally stimulated discharge measurements, while the latter results
not only from the improved thermal stability of the charges but also from the reduction in Young’s modulus of the PP ferroelectrets
due to the chemical modification as revealed by the dielectric resonance analyses. 相似文献
17.
A. Dutta J.K. Bhattacharjee B.K. Chakrabarti 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):97-103
We have discussed the zero-temperature quantum phase transition in n-component quantum rotor Hamiltonian in the presence of regular frustration in the interaction. The phase diagram consists
of ferromagnetic, helical and quantum paramagnetic phase, where the ferro-para and the helical-para phase boundary meets at
a multicritical point called a (d,m) quantum Lifshitz point where (d,m) indicates that the m of the d spatial dimensions incorporate frustration. We have studied the Hamiltonian in the vicinity of the quantum Lifshitz point
in the spherical limit and also studied the renormalisation group flow behaviour using standard momentum space renormalisation
technique (for finite n). In the spherical limit ()one finds that the helical phase does not exist in the presence of any nonvanishing quantum fluctuation for m =d though the quantum Lifshitz point exists for all d > 1+m/2, and the upper critical dimensionality is given by d
u
= 3 +m/2. The scaling behaviour in the neighbourhood of a quantum Lifshitz point in d dimensions is consistent with the behaviour near the classical Lifshitz point in (d+z) dimensions. The dynamical exponent of the quantum Hamiltonian z is unity in the case of anisotropic Lifshitz point (d>m) whereas z=2 in the case of isotropic Lifshitz point (d=m). We have evaluated all the exponents using the renormalisation flow equations along-with the scaling relations near the
quantum Lifshitz point. We have also obtained the exponents in the spherical limit (). It has also been shown that the exponents in the spherical model are all related to those of the corresponding Gaussian
model by Fisher renormalisation.
Received: 23 December 1997 / Received in final form: 6 January 1998 / Accepted: 7 January 1998 相似文献
18.
M. R. R. Gesualdi C. Jacinto T. Catunda M. Muramatsu V. Pilla 《Applied physics. B, Lasers and optics》2008,93(4):879-883
In this work, the light-induced lens effect due to thermal and/or photorefractive processes was studied in pyroelectric (undoped
and Fe2+-doped) lithium niobate crystals (LiNbO3) using thermal lens spectrometry with a two-beam (pump–probe) mode-mismatched configuration. The measurements were carried
out at two pump beam wavelengths (514.5 and 750 nm) to establish a full understanding of the present effects in this material
(thermal and/or photorefractive). We present an easy-to-implement method to determine quantitative values of the pyroelectric
coefficient (dP
s/dT), its contribution to the thermal effect and other thermo-optical parameters like thermal diffusivity (D), thermal conductivity (K) and temperature coefficient of the optical path length change (ds/dT). These measurements were performed in LiNbO3 and LiNbO3:Fe (0.1 ppm Fe2+) crystals with c axis along the direction of laser propagation. 相似文献
19.
The eight optical spectral band positions and three spin-Hamiltonian parameters (g factors g//, g⊥ and zero-field splitting D) of V2+ ions in trigonal CdCl2 crystal are calculated together from the complete diagonalisation (of energy matrix) method (CDM) based on the two-spin-orbit-parameter model (also called the cluster approach). In the model, differing from the usual one-spin-orbit-parameter model in the conventional crystal-field theory (where only the contribution to spin-Hamiltonian parameters due to the spin-orbit parameter of central dn ion is considered), both the contributions from the spin-orbit parameter of central dn ion and that of ligand ions are taken into account. The calculated results show reasonable agreement with the experimental values. The local lattice relaxation in the vicinity of V2+ ion due to the introduction of V2+ impurity is acquired from the calculations. The calculations of spin-Hamiltonian parameters from the CDM based on the one-spin-orbit-parameter and those from the perturbation theory method based on the two-spin-orbit-parameter model are also made for comparison. The results are discussed. 相似文献
20.
A. A. Lavrent’ev B. V. Gabrel’yan P. N. Shkumat B. B. Kulagin I. Ya. Nikiforov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(5):631-634
The electron-energy structure of the structure of monosulfides of 3d metals is calculated using a modified LAPW + lo technique that allows for the antiferromagnetic ordering in different crystallographic
layers. It is shown that the splitting of d-states of the transition metal with regard to the antiferromagnetic ordering in layers leads to a transition of VS, MnS,
CoS, NiS, and FeS monosulfides in the troilite structure from metallic to semiconducting state. 相似文献