Acoustic properties of marine animals forming deep scattering layers of the ocean

Acoustic models are considered for different animals that inhabit the deep scattering layers of the ocean and form a scattered acoustic field. These animals are divided into several groups that differ in their acoustic properties: fish with and without swim bladders, crustaceans, small squids, and other animals whose bodies consist of soft tissues and have no hard or gaseous inclusions. Normalized criteria are chosen for the quantitative comparison of the scattering properties of the animals. For the animals of each group, computational models are presented and analyzed. Generalized curves are constructed for the quantitative comparison of the backscattering cross sections of animals from different groups and of different sizes at different sound frequencies. In addition, these curves allow one to estimate the absolute values and the frequency characteristics of the scattering cross sections of animals for wide frequency and size ranges.     

1.30-2.21MeV质子在硅上的160°散射截面测量

采用薄靶对能量 1.30 - 2 .2 1MeV质子在纯度为 99.99%硅上的非卢瑟福弹性背散射截面(16 0°背散射角 )进行了测量 .质子束由 2× 1.7MV串列加速器提供 ,测量仪器采用金硅面垒探测能谱仪 .实验中最低能区进入卢瑟福弹性散射能区 ,测量结果与以前发表的结果进行了比较 .所测量数据可供从事背散射分析技术的有关人员参考 . The elastic backscattering cross sections of H + from silicon for a wide energy range are very useful parameters in the proton backscattering analysis for investigating silicon content and distribution profiles in the films. It is necessary to measure the scattering cross sections with good accuracy at a large scattering angle for the applications of proton backscattering analysis. The present paper reports our measured results of differential elastic backscattering cross sections of 1.30-2.21 MeV...     

Radar backscattering from Gerstner's sea surface wave

In the framework of a two-scale scattering model, radar backscattering from the rough sea surface was considered. The sea surface was modelled as a superposition of a nonlinear, large-scale Gerstner's wave and small-scale resonant Bragg scattering ripples. The zero-order diffracted field was found by a geometrical optics approach, with shadowing taken into account, and by an 'exact' solution of the diffraction problem obtained numerically. For vertical and horizontal polarizations, the spatial distribution of specific scattering cross sections along the large-scale wave was obtained. The spatially averaged specific backscattering cross sections, as well as the mean Doppler frequency shifts at both polarizations, obtained by the geometrical optics approach are compared with those obtained by using the 'exact' solution of the large-scale diffraction problem. The roles of shadowing and multiple wave scattering processes are discussed, and qualitative explanations of the difference between these two approaches are given.     

Search for the neutrino magnetic moment in the elastic νe scattering

The possibility of detecting the anomalous neutrino magnetic moment from comparison of the “electromagnetic” and “electroweak” contributions to the differential and total cross sections of neutrino-electron scattering is considered. The results of quantitative analysis and a graphical image of the cross sections are presented for the case of scattering of beryllium solar neutrinos by an electronic target.     

Cross section for 160° elastic scattering of 1.4–2.4 MeV protons from nitrogen and titanium

Differential elastic scattering cross sections for 1·4–2·4 MeV protons from natural nitrogen and titanium were measured at laboratory scattering angle 160°. The present cross section data are tabulated for later use in backscattering analyses. Our results for nitrogen are in qualitative agreement with previous data taken at slightly different scattering angles. The cross sections of titanium agree with theoretical Rutherford values within experimental errors. Examples of recent analytical applications of proton backscattering are given.The authors wish to thank the members of NPI accelerator group for their assistance in the course of experiments.     

Analysis of Scattering Properties from an Infinite Plasma Cylinder

In this paper, the scattering characteristics of an infinite plasma cylinder are studied theoretically by using the method of eigenfunction expansion. The backscattering cross sections of plasma cylinder in the transverse magnetic (TM) polarization case are calculated in detail. Effects of different parameters on the backscattering cross section are illustrated. Some errors in determining the complex wave number in plasma, as appeared in literatures published previously, are also rectified.     

Polarization dependency of enhanced multipath radar backscattering from an ocean-like surface

Previous analyses of electromagnetic scattering from a two-scale ocean surface assumed the tilts on a large-scale surface to be small. This means that multiple scattering between large-scale roughnesses is insignificant. If the tilts are not small, multipath-enhanced backscattering may occur due to quasi-specular reflections between the opposite slopes of a large-scale surface component. We have considered the simplest situation; this involves one reflection from the large-scale component and one single-scattering from the small-scale component. The coherent addition of this process to the reciprocally reverse one creates multipath-enhanced backscattering. The relative gain in the HH backscattering cross section up to the level of the VV signal was obtained for surface-wave slopes of about 30° and for large incidence angles. This gain occurs because the VV signal experiences an extinction during reflection at incident angles close to the pseudo-Brewster angle. The presented model provides insight into one scattering mechanism that is possibly responsible for the departure of radar sea experimental data from predictions by the conventional two-scale model.     

Wave diffraction by a concave statistically rough surface

We consider a statistically rough impedance surface that is concave on average in contrast to a plane. Backscattering from such a surface is considered based on the small perturbation theory method. The diffraction problem is divided into two parts which are considered separately: the problem of scattering by small roughness (assumed to be local) and the propagation of incident and scattered fields over a smooth large-scale concave surface. In contrast to the 'two-scale' scattering model, the zero-order unperturbed wavefield is not assumed to be specularly reflected from the local tangent plane to the smooth surface, but it is a solution of a corresponding diffraction problem. Two particular cases of smooth surfaces are considered: first, the inner surface of a concave cylinder with a constant radius and finite angular pattern, and second, a compound surface that consists of a coupled half-plane and the cylindrical surface mentioned above. In a geometrical optics limit and with propagation at low grazing angles, the analytical results for a zero-order (unperturbed) field are obtained for these two cases in the form of a series over multiple specular reflected fields. It is shown that these non-local processes lead to the essential increase in the backscattering cross section in comparison with the two-scale model and tangent-plane approach.     

Wave diffraction by a concave statistically rough surface

Abstract

We consider a statistically rough impedance surface that is concave on average in contrast to a plane. Backscattering from such a surface is considered based on the small perturbation theory method. The diffraction problem is divided into two parts which are considered separately: the problem of scattering by small roughness (assumed to be local) and the propagation of incident and scattered fields over a smooth large-scale concave surface. In contrast to the ‘two-scale’ scattering model, the zero-order unperturbed wavefield is not assumed to be specularly reflected from the local tangent plane to the smooth surface, but it is a solution of a corresponding diffraction problem. Two particular cases of smooth surfaces are considered: first, the inner surface of a concave cylinder with a constant radius and finite angular pattern, and second, a compound surface that consists of a coupled half-plane and the cylindrical surface mentioned above. In a geometrical optics limit and with propagation at low grazing angles, the analytical results for a zero-order (unperturbed) field are obtained for these two cases in the form of a series over multiple specular reflected fields. It is shown that these non-local processes lead to the essential increase in the backscattering cross section in comparison with the two-scale model and tangent-plane approach.     

碳对α的非卢瑟福背散射截面研究

报道了散射角为１７０°±１．５°，α粒子能量在５－９．０ＭｅＶ之间，ｃ的背散射截面的实验测量值；用Ｒ矩阵理论，通过与实验数据拟合，分析、给出了一套能级参数，并计算了能量范围在２－９．０ＭｅＶ，ｃ的背散射截面；讨论了对背散射分析感兴趣的窄而孤立的强共振峰４２５０±１０ＫｅＶ随靶厚、角度的变化关系以及截面变化缓慢的平坦区３．６－４．２０ＭｅＶ，６．４２５－６．７００ＭｅＶ能区的截面值与背散射角度的关系。 关键词：     

30-3000eV的正电子被O2、H2O及CH4散射的总截面计算

使用可加性规则，在Hartree-Fock水平上计算了30-3000eV的正电子被三个分子（O2、H2O及CH4）散射的总截面。计算正电子被三个分子散射的总截面时，首次使用了被束缚原子概念修正过的复光学势（这一复光学势考虑了分子中两个原子间的电子云重叠效应）。将正电子被这三个分子散射的总截面计算结果与实验结果及其它理论计算结果进行了比较，结果显示出在30-3000eV内，文中的计算结果与实验结果及其它理论计算结果具有较好的一致性。因此，可加性规则与修正后的复光学势相结合，完全适用于正电子被分子散射的总截面的计算。     

Discording power of Hamiltonian interactions

In this paper, we report the coherent scattering cross sections of some lanthanides at low momentum transfer in four angular ranges of (0°?4°), (0°?6°), (0°?8°) and for ²⁴¹Am (59.54 keV) and ¹³⁷Cs (661.6 keV) gamma rays. The coherent scattering cross sections were derived by subtracting the small contribution of the corresponding angle integrated incoherent scattering cross sections from the experimentally measured total (coherent + incoherent) scattering cross sections for the elements and energies of interest. The coherent scattering cross sections were found to agree with the corresponding theoretical cross sections within the range of experimental errors. The theoretical coherent scattering cross sections were computed by numerically integrating the S-matrix data of the elements in the angular ranges of interest. The incoherent scattering cross sections were based on the compilations which make use of the non-relativistic Hartree-Fock (NRHF) model for the atomic charge distribution.     

THE STUDIES OF NON-RUTHERFORD BACKSCATTERING CROSS SECTIONS OF 4He FROM 16O

In this article, we report the 170° backscattering cross sections of ⁴He from ¹⁶O in the energy range of 2.0-9.0 MeV. Our measurements show that the alpha-oxygen scattering remains Rutherford scattering up to E_α=2.35 MeV, and there exist two energy regions, namely 5.55-5.85MeV and 8.50-8.80MeV, where the cross sections are enhanced and show a smooth variation. The measured laboratory cross sections are 9.50-9.97 and 35.0-33.0 times greater than the Rutherford values, respectively. In the 8.50-8.80MeV region, the cross sections at scattering angles of 160°, 165°, 170° and 175° were measured and found to be strongly angle-dependent. A most strong resonance occurred at 7.60 MeV, where the cross section is 200 times of its Rutherford value. This resonance has been used to measure the ¹⁶O concentration on a Cu surface, with a sensitivity of 1×10¹⁵ oxygen atoms/cm², Besides, we have studied the backscattering angle dependence of the threshold energy, i.e., the energy at which the elastic cross section begins to deviate from its Rutherford value. The experimental result seems not in agreement with the prediction made from the analytical formula developed by Bozoian et al.     

微粗糙面上方球形粒子的光散射及其散射截面的计算

基于互易定理研究了光波入射时微粗糙面与其上方球形粒子复合模型的光散射。根据粗糙表面电流积分方程并利用表面微扰展开，得到了微粗糙面表面极化电流的迭代解，给出了耦合电场的计算方法。结合散射耦合场散射矩阵和已有的微粗糙面及球形粒子的散射矩阵，给出了复合模型散射截面的计算公式，数值计算了复合模型的后向散射截面并进行了详细讨论。     

Backscattering of s-polarized light from a cloud of small particles above a dielectric substrate

The scattering of s-polarized electromagnetic waves by a cloud of small particles above an interface is numerically studied, accounting for multiple scattering. The backscattering effect is first observed without the interface and the influence of the index of the particles is shown. In the case of a dilute system of particles with a low index such that no backscattering peak appears without the interface, it is shown that the introduction of an interface restores the backscattering effect. A physical mechanism responsible for this peak is described. In conclusion, a comparison of this model with scattering by rough surfaces is made.     

Diffractional Nuclear Processes Involving Composite Particles

The diffractional picture of nuclear processes at high energies involving composite particles is given. The solution of the Lippmann-Schwinger equation for the problem on scattering in the scattering center systems is considered in the high-energy approximation. The general formulas for the cross section of different diffractional processes with particle transmission are obtained. The effects of multiple scattering and their mutual compensation are discussed. The applicability conditions of the diffractional approach are discussed. The diffractional processes during the interaction of high-energy deuterons with nuclei are considered in detail. Without the assumption of deuteron size smallness compared to nuclear size, the cross sections of different diffractional processes are calculated with nuclear boundary diffusion taken into account. The nonmonotonic dependence of the diffractional disintegration cross section for deuterons on the mass number is shown due to the influence of nuclear boundary diffusion. The role of the diffractional and the Coulomb mechanisms of interaction depending on the nuclear mass number is discussed. The calculated dependences are compared with experimental data. The interference during the multiple scattering and its relationship with the diffractional structure of the angular scattering during the scattering on the composite systems are considered. The comparison the between diffractional approximation and different variations of the impulse approximation is made.     

A Correlation Potential Method for Electron Scattering Total Cross Section Calculations on Several Diatomic and Polyatomic Molecules over Energy Range 10 ～ 5000 eV

A complex optical model potential correlated by the concept of bonded atom, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the total cross sections for electron scattering on several molecules (NH₃, H₂O, CH₄, CO, N₂, O₂, and C₂H₄) over the energy range 10～5000 eV using the additivity rule model at Hartree-Fock level. The difference between the bonded atom and the free one in states is that the overlapping effect of electron clouds of bonded atoms in a molecule is considered. The quantitative total cross sections are compared with the experimental data and with the other calculations wherever available and good agreement is obtained over the energy range 10～5000 eV. It is shown that the correlated calculations are much closer to the available experimental data than the uncorrelated ones at lower energies, especially below 500 eV. Therefore, considering the overlapping effect of electron clouds in the complex optical model potential could be helpful for the better accuracy of the total cross section calculations of electron scattering from molecules.     

一种计算中、高能电子被分子散射总截面的修正势方法

在考虑分子内成键原子间的电子云重叠效应的基础上，提出了一种能够在中、高能区准确计算“电子-分子”散射总截面的修正势方法.利用可加性规则及Hartree-Fock波函数，使用这一修正过的复光学势，在30—5000eV内对电子被4个等电子(Z=18)分子(HCl，H₂S，PH₃和SiH₄)散射的总截面进行了计算，并将理论计算值与实验结果及其他理论值进行了比较.结果表明，利用这一修正过的复光学势及可加性规则进行计算，所得理论值与实验结果更为接近. 关键词： 电子散射 总截面 可加性规则 束缚原子     

Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies

A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges.