共查询到20条相似文献,搜索用时 312 毫秒
1.
Igor Alperovich Dooshaye Moonshiram Alexander Soldatov Yulia Pushkar 《Solid State Communications》2012,152(20):1880-1884
Density functional theory (DFT)-based relativistic calculations were performed to model the Ru L-edge X-ray absorption near edge structure (XANES) spectra of the hexaammineruthenium complex [Ru(NH3)6]3+ and “blue dimer” water oxidation catalyst, cis,cis- [(bpy)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+ (bpy is 2,2-bipyridine). Two computational approaches were compared: simulations without the core-hole and by modeling of the core-hole within the Z+1 approximation. Good agreement between calculated and experimental XANES spectra is achieved without including the core-hole. Simulations with algorithms beyond the Z+1 approximation were only possible in a framework of the scalar relativistic treatment. Time-dependent DFT (TD-DFT) was used to compute the Ru L-edge spectrum for [Ru(NH3)6]3+ model compound. Three different core-hole treatments were compared in a real-space full multiple scattering XANES modeling within the Green function formalism (implemented in the FEFF9.5 package) for the [Ru(Mebimpy)(bpm)(H2O)]2+ complex. The latter approaches worked well in cases where spin–orbit treatment of relativistic effects is not required. 相似文献
2.
W. Trombik W. Trautmann F. Krug W. Dünnweber D. Konnerth W. Hering R. Singh D. Zeppenfeld 《Physics letters. [Part B]》1984,135(4):271-274
Using the out-of-plane γ-ray particle coincidence method we have measured the spin alignment Pzz of excited 12C(2+) nuclei from 12C+12C inelastic scattering in the energy range 16 MeV ? Ecm ? 33 MeV.Pzz varies strongly as a function of energy and angle. The correlation of resonant structures in the cross section with maxima of the alignment is particularly clear in mutual inelastic scattering and in θcm = 90° single inelastic scattering. 相似文献
3.
R. Wichmann J. Ahrens H. J. Arends R. Beck G. Galler A. Hünger A. Kraus I. J. D. MacGregor J. Peise B. Seitz M. Schmitz M. Schneider O. Selke M. Schumacher F. Wissmann 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):169-177
High resolution proton energy spectra from the4He(γ,p) reaction have been measured with tagged photons in the range Eγ = 130?525 MeV using the large Mainz NaI(T1) spectrometer atΘ p lab =37.1°. Three separate reaction channels were identified, viz.4He(γ,p)t two-body breakup,4He photodisintegration via two-nucleon photon absorption processes and the quasifree pion production channel. Differential cross sections are presented for each of these channels as a function of photon energy. The sum of the two-nucleon photon absorption and the quasifree pion production differential cross sections, in the CM system, resembles that of the corresponding free-nucleon differential cross section when Fermi motion is taken into account. 相似文献
4.
We calculate the production cross section of Higgs-boson pairs ine + e ? annihilation. In this reaction the lowest order contribution comes from one loop graphs. We study the behaviour of the cross section as a function of the energy, the Higgs-boson mass and the scattering angle. 相似文献
5.
C. Spitaleri M. Aliotta P. Figuera M. Lattuada R.G. Pizzone S. Romano A. Tumino C. Rolfs L. Gialanella F. Strieder S. Cherubini A. Musumarra Đ. Miljanic S. Typel H.H. Wolter 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):181-187
The Trojan-horse method has been suggested as a means to study a two-body reaction at astrophysical energies via a three-body
breakup reaction. In order to test this method the 6Li(12C,α12C)2H reaction was studied in a kinematically complete experiment at an incident energy of 18 MeV. Coincidence spectra show the
presence of the quasi-free α-12C scattering process. The excitation function of the three-body reaction is calculated in the plane wave impulse approximation
assuming quasi-free scattering and is compared with the experimental data. Also, the excitation function of the virtual α-12C elastic scattering is extracted from the three-body reaction cross section at low deuteron momenta and compared with the
behaviour of the free scattering cross section.
Received: 4 June 1999 / Revised version: 15 November 1999 相似文献
6.
The reaction cross section σRpA(E) for proton-nucleus collisions varies with energy as the total cross section σtpN(E) does for proton-nucleon scattering in the energy regime 100 MeV ? E ?400 GeV. We propose several empirical relations, and test them by a χ2 analysis of various data. Within the framework of Glauber theory, the parameters in the relations can be linked to the cross section for a single inelastic collision. 相似文献
7.
W. Erlewein M. von Seggern Dr. J. P. Toennies 《Zeitschrift für Physik A Hadrons and Nuclei》1968,211(1):35-50
Cross sections for scattering of N2 (j=0) molecules on He atoms have been calculated for relative energies below 5 · 10?3 eV (58 °K). The time independent scattering formalism ofArthurs andDalgarno was used together with an assumed Lennard-Jones type potential with anisotropicP 2(cos?) terms in the attractive and repulsive parts. The resulting system of coupled differential equations was solved in the distorted wave and close coupling approximations for the differential and integral cross sections for elastic and inelastic (j=0→j=2) scattering. In the integral inelastic cross section several sharp resonances were found to contribute 40% to the cross section at energies below 40 °K. The resonance peaks are attributed to orbiting or short-lived compound states since they are also observed in the elastic cross section at energies which are lower by the excitation energy of 1.5 · 10?3 eV. Finally, the effect of varying the potential parameters on the integral inelastic cross section was studied at 50 °K and a rough formula for the cross section as a function of the parameters is obtained. The formula shows that a certain ratio of repulsive and attractive anisotropies leads to a small inelastic cross section indicating a mutual cancellation. 相似文献
8.
T. L. Enik V. A. Ermakov R. V. Kharjuzov L. V. Mitsyna V. G. Nikolenko S. S. Parzhitski A. B. Popov G. S. Samosvat V. A. Vtjurin 《Physics of Atomic Nuclei》2003,66(1):56-60
As a preparation for the new experiment to measure the ne scattering length ane the total neutron cross section of gaseous argon has been obtained by the time-of-flight method at the Dubna booster IBR-30 in the energy range from ~5 eV to ~30 keV. A combined one-level analysis of the newly obtained and other known data on cross sections of Ar and 36Ar has made it possible to improve some neutron parameters and calculate the scattering cross section σs and the scattering length a separately for 36Ar and 40Ar at any energy. 相似文献
9.
N. B. Ladygina 《Few-Body Systems》2012,53(3-4):253-265
The dd → 3 Hen reaction is considered at the energies between 200 and 520?MeV. The Alt–Grassberger–Sandhas equations are iterated up to the lowest order terms over the nucleon–nucleon t-matrix. The parameterized 3 He wave function including five components is used. The angular dependence of the differential cross section and energy dependence of tensor analyzing power T 20 at the zero scattering angle are presented in comparison with the experimental data. 相似文献
10.
A. D. Fedoseev 《Journal of Experimental and Theoretical Physics》2014,119(3):573-578
The partial differential cross section of inelastic magnetic neutron scattering from the compound LaCoO3 in the paramagnetic phase is studied theoretically. The contribution to scattering from the high-spin state of an ion in zero magnetic field and the modification of this contribution upon application of a magnetic field are calculated using the effective Hamiltonian for the 5 D term. The amplitude of the peak in the dependence of the scattering cross section on the energy of scattered neutrons, which corresponds to the transition from the low-spin to the intermediate-spin state, is estimated. 相似文献
11.
An approach which makes the first order pion-nucleus optical potential theoretically sound is presented. This study should permit higher order improvements to the potential to be more meaningful and the nuclear structure information extracted from pi-nucleus scattering to be more reliable. Based on multiple scattering theory, three optical potentials are constructed and studied in momentum space. These models are the popular Kisslinger potential, the local “Laplacian” potential, and an “improved off-shell potential;” the latter one is derived from absorptive separable pion-nucleon potentials which exactly reproduce on-shell πN scattering. By working in momentum space and explicitly including πN resonances and off-shell effects in the definition of the optical potential, the approach described here is capable of handling any number of pi-nucleon partial waves, is applicable over a very wide energy region, is based on a physical model for off-shell behavior, and is extended easily to include higher order effects. The optical potentials are inserted into two different relativistic wave equations to determine the total cross section and elastic differential cross section for pi-nucleus scattering. It is found that the various models for off-shell πN scattering determine significantly different πC12 scattering, with the improved off-shell model preferred on theoretical grounds. Also discussed is the importance of properly transforming πN scattering to the pi-nucleus c.m. system, the origin of the shift in the peak position of the π?C total cross section, and the reason for the increased diffractive nature of the differential cross section at 180 MeV. 相似文献
12.
We calculate the contribution from order parameter fluctuations to the light scattering cross section in 4He near Tλ including effects from order parameter relaxation. The existence of a central dip in the critical region is discussed. 相似文献
13.
A nonrelativistic deuteron wave function involving the D-wave state and having a correct asymptotic behavior is constructed on the basis of the experimentally measured deuteron charge form factor G C(q) and deuteron structure function A(q). The differential cross section for elastic deuteron-nucleus scattering is calculated by using this wave function and is found to agree with experimental data at an energy of 110 MeV. Integrated cross sections for various processes involving deuteron-nucleus interactions are also calculated. The distribution in the emission angle of the center of mass of the neutron-proton system produced in the diffractive dissociation of 110-MeV deuterons in the field of 208Pb nuclei is obtained. 相似文献
14.
Phase shifts for d-α elastic scattering have been extracted from differential cross sections and the vector and tensor analysing powers of 4He(, d)4He scattering in the energy range from 3 to 17 MeV. The angular momenta were restricted to L ≦ 4 and mixing parameters ε1 and ε2. Good fits could be obtained to nearly all the experimental data analysed. The total reaction cross section and polarization-transfer coefficients were predicted and compared with the measured data; satisfactory agreement was found within the experimental errors. Evidence for a new resonance was found between 11 and 15 MeV. 相似文献
15.
Joseph Callaway 《Physics letters. A》1984,100(8):415-418
The scattering of electrons by hydrogen atoms is studied for an incident energy of 15 eV, by means of a close coupling calculation using a pseudostate basis. Results are presented for elastic scattering and n = 2 excitation, including angular correlation parameters. The ionization cross section is extracted by an improved projection technique. 相似文献
16.
The total cross sections for positron impact on hydrocarbons have been calculated using the additivity rule in which the total
cross section for a molecule is the sum of the total cross section for the constituent atoms. The energy range considered
is from a few eV to several thousand eV. The total cross sections for positron impact on an atom are calculated by employing
a complex spherical potential which comprises of a static, polarization and an absorption potential. We have good agreement
with the experimental results for hydrocarbons for positron energy ⩾100 eV. Our results also agree with the available calculations
for CH4 and C2H2 which employed full molecular wavefunctions beyond 100 eV. Our absorption cross sections also agree with molecular wave-function
calculations for C2H2 and CH4 beyond 100 eV. We have shown the Bethe plots fore
+−C ande
+−H scattering systems and Bethe parameters have been extracted. We have fitted the cross section for positron impact on hydrocarbons
in the formσ
t(C
n
H
m
)=naE
−
b+mcE
−
d in the energy range 300–5000 eV wherea=195.0543,b=0.7986,c=371.1757 andd=1.1379 withE in eV andσ
t in 10−16 cm2. 相似文献
17.
M. Trefz Amand Faessler W.H. Dickhoff M. Rhoades-Brown 《Physics letters. [Part B]》1984,149(6):459-464
The contribution to the real and imaginary nucleus-nucleus (N-N) optical potential from nucleon-nucleon scattering in the medium is calculated in a local density approximation from a two Fermi sphere nuclear matter picture for the N-N collision. This reaction mechanism is shown to be dominant for 12C + 12C scattering at all considered energies (160 MeV < Elab < 2250 MeV) giving a weakly energy dependent reaction cross section of about 900 mb. Inclusion of the collective 2+, 3? excitations in a coupled channel calculations gives good agreement for both the measured elastic and inelastic 2+ cross section at Elab = 1016 MeV. This fully microscopic parameter free calculation indicates that the energy dependence of the reaction cross section for this system is mostly due to the decrease of the collective contribution with increasing energy contrary to current theoretical models. 相似文献
18.
19.
We show that a growth of the proton-proton total cross section with energy can be entirely attributed to the purely perturbative mechanism. The infrared regularization at rather short distances R c ? 0.3 fm allows extending the BFKL technique from deep inelastic to hadron-hadron scattering. With the inclusion of the absorption corrections our results are in agreement with the LHC data on σ tot pp . 相似文献
20.
Neutron transmission experiments and determinations of coherent scattering lengths were performed on natural chromium and enriched samples of50Cr,52Cr,53Cr and54Cr. By means of the Christiansen-filter-technique we obtained new values for the scattering lengths of the bound atoms:b(natCr)=3.635±0.007 fm,b(50Cr)=?4.50±0.05 fm,b(52Cr)=4.914±0.015 fm,b(53Cr)=?4.20±0.03 fm, andb(54Cr)=4.55±0.10 fm. The transmission experiments with neutrons of 510 ΜeV, 1.26 eV and 5.19 eV energy resulted in data for the absorption cross sectionσ a (natCr) =3.05±0.08 b and for the scattering cross section at “zero energy”:σ 0 (natCr)=3.381±0.010 b. Data for incoherent and spin-state scattering and for the potential-scattering radius of the nuclei could be deduced from these results. 相似文献