A modified RPA for open-shell nuclei

A modified RPA suitable for open-shell nuclei is constructed using the Green function method. Unlike the standard RPA, this modification makes allowance for the spread of bound single-particle and single-hole states over more complex configurations which is done due to a more realistic approximation of single-particle Green functions. The calculations of the nucleon-nucleus S-matrix and of the probability amplitudes for the single-particle transitions of the nucleus from the ground state into scattering states are examined. For the separable effective forces these quantities are expressed in closed form.     

Microscopic description of low-energy neutron scattering by nuclei

The Bloch and Gillet shell-model formalism extended to continuum states is applied to lowenergy neutron scattering by nuclei. It is shown that complete antisymmetrization leads in the r-representation to corrective terms which yield important corrections to the scattering lengths. Calculations are performed within a model restricted configuration space for the target nuclei ¹²C, ¹³C, ¹⁶O, ¹⁷O and ⁴⁰Ca. We predict values for the spin-dependent scattering amplitude for ¹³C and ¹⁷O. The antisymmetrization problem in the case of a large configuration mixing is studied for the ¹⁹F target nucleus. The resonant effects of the compound nucleus are then very important and the results become very sensitive to the configuration space and the interaction parameters.     

6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发,得到同时包含实部和虚部的核子-核散射的微观光学势,并利用折叠模型直接获得了核一核散射参数无关的整体微观光学势.考虑到核.核散射去弹过程高级项的贡献和6Li的碎裂效应,在微观光学势的实部和虚部中引入了修正因子NR,N1.系统研究了入射粒子6Li与靶核12C,28Si,40Ca,58Ni,90Zr和208Pb散射的微观光学势,计算中虚部增强因子取N1≈3.0,而实部修正因子NR对于给定的碰撞系统几乎是一个常数.理论很好地再现了所有被研究靶核和入射能量的弹性散射实验数据.参数无关的微观理论对核.核散射,尤其是对不稳定核.核系统反应的描述是有价值的.     

Microscopic structure of nuclei from scattering through isobaric analogue resonances

Microscopic nuclear structure information that can be reached by proton scattering through isobaric analogue resonances (IAR) is discussed, mainly within the framework of weak-coupling. The concept of isospin for unbound states is examined. A critical evaluation of the methods for extracting nuclear structure information from the experimental results (such as excitation functions, angular distributions, etc.) is given. The mass regions that are studied in detail are the Pb-region and the N = 82 neutron single-closed shell nuclei. Attention is given to the comparison between weak-coupling calculations and experimental results supporting this concept in many nuclei. Level schemes as well as proton partial decay widths and angular distributions have been calculated and compared with the existing data concerning the proton decay of IAR. The concept of generalized neutron particle-hole (GNPH) state is introduced and its occurence extensively discussed within the Pb-region and N = 82 nuclei.     

On the theory of multiple scattering

In this paper a kinetic equation is derived for the distribution function in the variable q=2 sin(ϑ/2) for the case of a scattering cross section of general form under the assumption that the region of multiple scattering (the diffusion region) is small. The limits of the kinetic equation are discussed, with no restrictions imposed on the scattering angles. It is found that the equation has a solution in the form of an integral. Finally, it is established that the solution is applicable over the entire range of angles, from 0 to 180°. Zh. éksp. Teor. Fiz. 116, 418–435 (August 1999)     

6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发,得到同时包含实部和虚部的核子-核散射的微观光学势,并利用折叠模型直接获得了核-核散射参数无关的整体微观光学势.考虑到核-核散射去弹过程高级项的贡献和⁶Li的碎裂效应,在微观光学势的实部和虚部中引入了修正因子N_R,N_I.系统研究了入射粒子⁶Li与靶核¹²C,²⁸Si,关键词： 弹性散射 Dirac-Brueckner-Hartree-Fock方法 折叠模型 微观光学势     

6Li与核弹性散射的微观光学势

从基本的Dirac-Brueckner-Hartree-Fock微观理论出发，得到同时包含实部和虚部的核子-核散射的微观光学势，并利用折叠模型直接获得了核-核散射参数无关的整体微观光学势.考虑到核-核散射去弹过程高级项的贡献和⁶Li的碎裂效应，在微观光学势的实部和虚部中引入了修正因子N_R，N_I.系统研究了入射粒子⁶Li与靶核¹²C，²⁸Si，相似文献   

On the theory of multiple scattering II. Critical scattering

The systematic theory of multiple scattering which we gave in a previous paper is further elaborated for critical scattering. It is shown that in each order the multiple-scattering intensity near the critical point is in essence a contraction of consecutive uncorrelated single-scattering intensities. The anomaly of the critical depolarization factor is calculated and is found to be in quantitative agreement with recent experimental results. Double scattering corrections to the Ornstein-Zernike plot are discussed.     

Microscopic analysis of the elastic scattering of 11Li neutron-rich nuclei on protons

Amicroscopic optical potential is used to calculate cross sections for elastic ¹¹Li +p scattering at the energies of 62, 68.4, and 75 MeV per nucleon, and the results are compared with available experimental data. The potential used does not involve free parameters, but the depths of its real and imaginary parts are renormalized. The known trend in the energy dependence of the volume integrals of the optical potential is taken into account in analyzing experimental data. The role of spin-orbit interaction is studied, and the total reaction cross sections that are proposed to be measured in future experiments are calculated.     

On the theory of multiple scattering I

A systematic theory of multiple scattering is given for a nonpolar fluid of point dipoles. Local-field correction factors are consistently accounted for to all orders. To first order (single scattering) Einstein's result is obtained; the theory yields, however, automatically to this order the attenuation of the incoming beam before and of the scattered light after scattering. In the usual theories these effects are hidden in secular (shadow) contributions to multiple scattering. The single-triple and double-scattering intensities are briefly discussed.     

Analytical multiple scattering extension of the mie theory

Multiple scattering of light in aerosol is described in a simple picture within the framework of the Mie theory. Our approach leads to an analytical expression of the n-fold scattered electromagnetic field and then to a generalization of the optical parameters. The multiple scattering contributions are calculated avoiding the convergency and stability problems which are often encountered in standard numerical approaches. These problems occur due to the large number of events that have to be taken into account when large optical depths and/or a low signal to noise level exists. Such conditions are frequently encountered in atmospheric measurements.     

Relativistic multiple scattering theory of electrons by ferromagnets

In view of investigating for 3d- and 4f-ferromagnetic crystals the elastic scattering and the emission of polarized low-energy electrons as well as the bulk electronic structure, a relativistic multiple scattering theory has been developed, in which the exchange interaction with the magnetic ground state electrons is treated in a local density functional approximation. In a layer-KKR-type approach, the Dirac equation, which contains an effective magnetic field term, is first solved for a single crystal atom and subsequently for a monoatomic layer and for a semi-infinite crystal. Spin-orbit coupling and magnetic exchange interaction are thus simultaneously taken into account.     

Shell model theory of elastic scattering of nucleons by deformed nuclei

The escape width originating from a collective rotational state as a doorway state is calculated in the framework of the shell model theory of nuclear reactions. The rotational states are constructed by Yoccoz-Peierls angular momentum projection from deformed intrinsic states which are described by BCS wave functions. For some rare earth nuclei it is shown that there result escape widths of the order of magnitude of 20–100 keV.     

Microscopic absorptive interaction for composite finite nuclei

The theoretical framework for the microscopic calculation of an effective interaction of two composite nuclei is developed by applying Feshbach's projection operator formalism. Both translational invariance and the Pauli principle are taken into account exactly. The theory is based on model wavefunctions for finite nuclei and does not require nuclear matter approximations. The model Q-space consists of channels in which one or both nuclei are excited. A 1p1h-excitation mechanism is considered in some detail and the properties of an effective absorptive interaction are studied for the α-α-system as an example.