共查询到9条相似文献,搜索用时 0 毫秒
1.
P P Singh Q Li P Schwandt W W Jacobs M Saber E J Stephenson A Saxena S Kailas 《Pramana》1986,27(6):747-760
Differential cross-section angular distributions for the elastic scattering of 270 MeV3He particles from58Ni,90Zr,116Sn and208Pb have been measured. Optical model analysis of the cross-sections has yielded the optical model parameters for3He particles at 270 MeV. Angular distributions have also been measured for the inelastic excitation of the low-lying levels
in the above mentioned nuclei. A collective model analysis using the distorted wave Born approximation (DWBA) of these cross-sections
with the distorted waves generated by the optical model parameters determined from the elastic scattering analysis, has yielded
the reduced transition probability (B(EL)) values consistent with those reported in the literature. 相似文献
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3.
The analytic properties of scattering amplitudes provide important information. Besides the cuts, the poles and zeros on the different Riemann sheets determine the global behavior of the amplitude on the physical axis. Pole positions and residues allow for a parameterization of resonances in a well-defined way, free of assumptions for the background and energy dependence of the resonance part. This is a necessary condition to relate resonance contributions in different reactions. In the present study, we determine the pole structure of pion–nucleon scattering in an analytic model based on meson exchange. For this, the sheet structure of the amplitude is determined. To show the precision of the resonance extraction and discuss phenomena such as resonance interference, we discuss the S11 amplitude in greater detail. 相似文献
4.
DONG ZhengChao 《理论物理通讯》2000,33(1):55-62
An analytical Green's function approach to the study of the electronic transport in a magnetic sandwich structure is presented. Taking into account the quantum size effect and considering three types of scattering from bulk impurities, rough surface, and two rough interfaces, we calculate the one-particle Green's function and the in-plane conductivity, yield a new formula for conductivity. It is found that (i). the magnetoresistance in the ultrathin spin-value sandwiches shows oscillation as a function of thickness with a period of half Fermi wavelength; (ii) in the thin-film limit and the lowest-order approximation of the surface and interface scatterings, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities, surfaces and interfaces are additive. 相似文献
5.
Evolution of electric‐field‐induced quasibound states and resonances in one‐dimensional open quantum systems 下载免费PDF全文
O. Olendski 《Annalen der Physik》2017,529(3)
A comparative analysis of three different time‐independent approaches to studying open quantum structures in a uniform electric field was performed using the example of a one‐dimensional attractive or repulsive δ‐potential and the surface that supports the Robin boundary condition. The three considered methods exploit different properties of the scattering matrix as a function of energy E: its poles, real values, and zeros of the second derivative of its phase. The essential feature of the method of zeroing the resolvent, which produces complex energies, is the unlimited growth of the wave function at infinity, which is, however, eliminated by the time‐dependent interpretation. The real energies at which the unitary scattering matrix becomes real correspond to the largest possible distortion, , or its absence at which in either case leads to the formation of quasibound states. Depending on their response to the increasing electric intensity, two types of field‐induced positive energy quasibound levels are identified: electron‐ and hole‐like states. Their evolution and interaction in the enlarging field lead ultimately to the coalescence of pairs of opposite states, with concomitant divergence of the associated dipole moments in what is construed as an electric breakdown of the structure. The characteristic features of the coalescence fields and energies are calculated and the behavior of the levels in their vicinity is analyzed. Similarities between the different approaches and their peculiarities are highlighted; in particular, for the zero‐field bound state in the limit of the vanishing , all three methods produce the same results, with their outcomes deviating from each other according to growing electric intensity. The significance of the zero‐field spatial symmetry for the formation, number, and evolution of the electron‐ and hole‐like states, and the interaction between them, is underlined by comparing outcomes for the symmetric δ geometry and asymmetric Robin wall.
6.
The variation of fusion cross-section (σJfus) with energy in the12C+12C collision is linked to the underlying resonance phenomenon through the behavior of reaction cross-section (σ) of which σfus is taken as a part. The calculation of σfus is done through an energy-dependent imaginary potential in the optical model potential (OMP). Through dispersion relation,
such an imaginary potential gives rise to energy-dependent real potential which is incorporated in the OMP. In our calculation,
a form of potential for the nuclear part which has a soft repulsive in-built core is introduced based on similar works done
earlier. The calculated results of σfus are used to explain the oscillatory structure, astrophysical S-factor and the decreasing trend at higher energies of the
experimental σfus data in the case of12C+12C system with remarkable success. The potential used for fusion calculation is tested for fitting elastic scattering data
at some energies and is found good in forward angles. Further improvement of the fitting of these data is obtained by incorporating
a coupling potential in the surface region. About twenty resonances are observed in our calculation in the specific partial
waves and some of them are found close to the experimentally identified resonances in12C+12C reaction. Thus, we provide an integrated and comprehensive analysis of fusion, resonance and scattering data in the best
studied case of12C+12C reaction within the framework of optical potential model. 相似文献
7.
A. Hünger J. Peise A. Robbiano J. Ahrens I. Anthony H. -J. Arends R. Beck G. P. Capitani B. Dolbilkin H. Falkenberg G. Galler S. J. Hall J. D. Kellie R. Kondratjev R. Kordsmeier V. Lisin A. I. L''vov G. J. Miller C. Molinari P. Ottonello A. R. Reolon M. Sanzone M. Schmitz M. Schneider M. Schumacher O. Selke Th. Walcher F. Wissmann S. Wolf A. Zucchiatti 《Nuclear Physics A》1997,620(4):385-416
Differential cross sections for Compton scattering by the proton have been measured in the energy interval between 200 and 500 MeV at scattering angles of θcms = 75° and θcms = 90° using the CATS, the CATS/TRAJAN, and the COPP setups with the Glasgow Tagger at MAMI (Mainz). The data are compared with predictions from dispersion theory using photo-meson amplitudes from the recent VPI solution SM95. The experiment and the theoretical procedure are described in detail. It is found that the experiment and predictions are in agreement as far as the energy dependence of the differential cross sections in the Δ-range is concerned. However, there is evidence that a scaling down of the resonance part of the M1+3/2 photo-meson amplitude by (2.8 ± 0.9)% is required in comparison with the VPI analysis. The deduced value of the M1+3/2-photoproduction amplitude at the resonance energy of 320 MeV is: |M1+3/2| = (39.6 ± 0.4) × 10−3 mπ+−1. 相似文献
8.
Z. Liu X. Sun X. Zhou X. Lei Y. Guo Y. Zhang X. Chen H. Jin Y. Luo S.X. Wen C.X. Yang G.J. Yuan G.S. Li X.A. Liu W.D. Luo Y.S. Chen 《The European Physical Journal A - Hadrons and Nuclei》1998,1(2):125-135
High-spin states of 117Xe were investigated by means of in-beam γ-ray spectroscopic techniques via the reaction of 28Si bombarding a 92Mo target at beam energies of 100-120 MeV. A positive-parity rotational band decaying into the yrast negative-parity band
by a series of enhanced E1 transitions was observed for the first time, implying the existence of octupole correlations in
117Xe. The B(E1) values increase with spin. The νd5/2 band was firmly established up to 27/2+ and the B(M1)/B(E2) ratios were extracted from the relative intensities of γ-rays in this band. The previously known νh11/2 and νg7/2 [413]5/2+α=−1/2 bands were confirmed and extended up to high spins and two bandcrossings are observed in the latter at ħω=0.33 and
0.44 MeV, respectively. The bandcrossings and configurations of these bands are discussed by TRS and CSM calculations. In
a γ–γ–t measurement, the 11/2− and 7/2− levels were identified as two isomers with half-lives of 59.4±20 ns and 16.5±8.0 ns, respectively.
Received: 17 June 1997 / Revised version: 29 September 1997 相似文献
9.
D. Gamermann E. Oset D. Strottman M.J. Vicente Vacas 《Progress in Particle and Nuclear Physics》2008,61(1):153-154
We briefly present our model for generating open and hidden charm resonances and present the most interesting results. 相似文献