Absolute differential bremsstrahlung cross section for the scattering of 0.6-keV electrons by xenon atoms

The spectral distribution of the absolute differential cross section for total bremsstrahlung, including ordinary and polarization, for the scattering of 0.6-keV electrons from free xenon atoms has been measured. The bremsstrahlung photons have been detected at an angle of 97° with respect to the electron motion direction. The investigations have been carried out in the ultrasoft x-ray spectral region 60–240 eV. The results are compared with the total cross sections for bremsstrahlung calculated in several approximations for the scattering of 5-and 25-keV electrons by Xe atoms. Both the value and the spectral distribution of the experimental absolute cross sections are most satisfactorily reproduced by the calculations in the distorted partial wave approximation.     

Steady-state differential cross section for elastic scattering

Lower limits are found on the differential cross section for elastic scattering and on its derivatives with respect to the momentum transfer t at t = 0 at high energies on the basis of completely general considerations. The results are expressed in terms of the measurable total cross sections.Translated from Izvestiya VUZ. Fizika, No. 4, pp. 103–108, April, 1970.     

Differential cross section for elastic π± helium isotopes scattering from 25 to 65 MeV

Measurements of absolute elastic-scattering differential cross sections for π^±He at T^lab_π = 30.2 MeV, 45.1 MeV and 65.0 MeV and for π^±-⁴?⁴He at T^lab_π = 25.1 MeV and 51.1 MeV have been made in the angular range 40° to 145°. An overall accuracy of about ±5% was achieved. The results are compared with available theoretical calculations.     

A new “parametrization” of the differential cross section for elastic scattering

A new parametrization of the differential cross section for elastic scattering is proposed. The parametrization incorporates correct analytic properties of the differential cross section and is based on optimized polynomial expansions of an analytic function. It is, in principle, valid for all energies and all angles. The parametrization has been tested for pp, $\text{p}\text{p}$, pd, π^± and K^±p elastic scattering at high energies and small angles. The results of the new fits are compared with those of the old ones. It has been found that with the same number of parameters one obtains practically the same values of χ². However, the new values of physical quantities, such as slope, α and (dσ/dt)₀, in most cases differ considerably from those obtained by the old parametrization. In particular, it has been found that the slope of the differential cross section for pp, $\text{p}\text{p}$, pd and K^±p elastic scattering increases continuously as the forward direction is approached.     

Model differential cross section of elastic scattering of electrons by atoms in the Monte Carlo simulation of the passage of electrons in a substance

A new model differential cross section is proposed for describing elastic scattering of electrons in simulating the passage of electrons through a substance by the Monte Carlo method. This differential cross section correctly describes the first and second transport scattering cross sections, but is characterized by the total elastic scattering cross section much smaller than the actual value of the total elastic scattering cross section. The application of this differential cross section makes it possible to considerably reduce the number of elastic collisions in the Monte Carlo simulation of passage of electrons in a substance and to model the passage of high-energy electrons using the individual collision model.     

Reconstruction of the scattering potential from the high-energy differential cross section

A simple equation is derived for use in reconstructing the scattering potential from the angular distribution of scattered particles at a given energy. This equation is useful in the classical approximation of small angles and in the semiclassical quantum-mechanical treatment. Experimental data and this equation are used to reconstruct the interaction potentials for the scattering of helium, neon, and argon ions by atoms from the same group in various combinations, at 25, 50, and 100 keV. The simplicity of the equation allows potentials to be found at distances larger than were found previously by Everhart and Lane and with a smaller error in the approximate numerical calculations.Translated from Izvestiya VUZ. Fizika, No. 8, pp. 118–123, August, 1970.The authors thank O. M. Tsoi for assistance in the numerical calculations.     

Differential cross section surfaces for low energy scattering of electrons and positrons from rare gas atoms

The differential cross sections for scattering of electrons and positrons from He, Ne, Ar, Kr, and Xe at projectile energies below the inelastic thresholds are calculated using a model potential approach in which the interaction between the projectile and the target atom is partitioned into static, exchange (for electrons), and correlation-polarization parts. Two different forms of the parameter-free correlation-polarization potential are suggested; in both cases the correlation-polarization potential is determined by smoothly matching the asymptotic form of the polarization potential (1/r ⁴) to the correlation potential at the outermost orbital radius of the target atom. The results of angular distributions are presented in the form of contours of constant differential cross sections as well as in the form of differential cross section surfaces in three-dimensional plots. Both of these presentations display the locations of the principal maxima and minima of the differential cross sections as well as the critical points in a very useful manner.     

Differential cross section minima for elastic scattering of electrons by krypton atoms in the energy range 0–500 eV

Technical Physics - Elastic scattering of 0-to 500-eV electrons by krypton atoms is studied in terms of a model of phenomenological real potential with allowance for spin-orbit interaction. The...     

中高能电子被氟代甲烷散射的总截面计算

利用可加性规则,使用Hartree-Fock 波函数,采用被束缚原子概念修正过的复光学势,首次在100～5 000eV内对电子被具有较多电子数的氟代甲烷分子散射的总截面进行了计算,且将计算值与实验值及经验公式进行了比较,得出了被束缚原子概念修正过的复光学势可成功用于"电子-氟代甲烷"散射总截面计算的结论;研究了"电子-氟代甲烷"的散射总截面与目标分子总电子数及电子入射能量间的关系,初步分析了结构因子与总电荷数相关的原因,并指出了对复光学势进行进一步修正时应遵循的原则.     

屏蔽效应对氦原子(e,2e)反应中二重微分截面和单微分截面的影响

用DS3C模型计算了入射能为32.5, 36.5, 40.7 eV时电子入射单电离氦原子的二重微分散射截面, 并把计算结果与实验结果进行了比较, 对屏蔽效应进行了分析. 通过对二重微分散射截面在全空间的角度积分得到了电子入射单电离氦原子的单微分散射截面, 利用3C模型和DS3C模型计算了入射能为32.5, 36.5, 40.7, 50 eV时氦原子的单微分散射截面, 并把计算结果与实验结果进行了比较. 对截面的结构进行了分析, 并系统研究了交换效应对截面的贡献. 关键词： DS3C模型 二重微分散射截面 单微分散射截面 屏蔽效应     

Small-angle elastic scattering of 14.8 mev neutrons

The 14.8 MeV neutron elastic scattering differential cross sections of U, Pb, Hg, Ta, Sn and Al have been measured for angles extending from 10° down to 1.8° and for U and Pb down to 0.35°. Nuclear cross sections extrapolated to 0° have been compared with the Wick limit. The U nuclear cross sections did not rise as sharply toward 0°, and were not in as serious disagreement with the spherical optical model, as in earlier measurements. The smallest-angle data verified the Schwinger prediction.     

Inelastic scattering of electrons by helium

Measurements of the angular distribution and total cross section for all inelastic processes in the scattering of intermediate and high energy electrons by helium atoms are analyzed using the first Born approximation.     

Small-angle elastic scattering of 2.5 MeV neutrons

Differential cross sections and asymmetries of 2.50 MeV polarized neutrons elastically scattered by In, Ho, Hg, Bi and U have been determined for scattering angles from 2.1° to 9.1°. The measurements were carried out by the use of a neutron positional spectrometer. The results, when compared with the predictions of the electromagnetic interaction, indicate some deviation of 〈σ(θ)P(θ)〉 from the expected values. The observed cross sections are systematically greater than those evaluated within the framework of the optical model.     

Triple differential cross section for autoionisation of helium by electron impact at 100 eV

Cross sections for autoionisation of helium by electron impact have been measured by an electron-electron coincidence technique at an incident electron energy of 100 eV and a scattering angle of 15°. The variation of the direct ionisation cross section and the resonance parameters for the (2s2p)¹P autoionising level, as functions of ejected electron angle, are compared with the results of recent theoretical calculations.     

(e, 2e) triple differential cross section for ionization-excitation of helium

Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation. The wave function of the low energy ejected electron is obtained in the field of residual He⁺ ion in 2s-state. The calculation has been done for the processe ⁻+He→e ⁻+He⁺(2s)+e ⁻ in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and the results are compared with the absolute experimental data of Dupreet al [J. Phys. B25, 259 (1992)] at ∼ 5.5 keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak intensity by about 30% over the first Born results and thus to bring it closer to the experimental data.     

The shrinkage of the elastic differential cross section from the multiperipheral model using unitarity

The overlap function has been calculated analytically from a simplified Chan-?oskiewicz-Allison (C?A) model with Regge phase. Hamer and Peierls have shown using the impact parameter variables that in the C?A model with Regge phase the slope of the overlap function increases too rapidly with total energy when compared to experiments. According to Jadach and Turnau this was due to inadequate approximations made for the norm of the C?A amplitude and they showed that in the C?A model with no momentum-dependent phase the shrinkage agrees with experiments but the magnitude of the slope is too small. We show without making the inadequate approximations mentioned by Jadach and Turnau that when the Regge phase is used in the C?A model; it makes the overlap function shrink too rapidly and have a too large slope above 20 GeV/c. Clustering will improve the agreement with experiments, especially when one further assumes that the clusters do not form resonances. Then the trajectories which are exchanged between two clusters are exchange degenerate and have a real contribution to the amplitude. The analytic calculations make it possible to discuss contributions to the overlap function from various properties of the production amplitude.     

Inelastic scattering of fast electrons from metastable states of helium

Inelastic scattering cross sections for collisions of electrons with helium atoms in metastable 2 ^1,3 S states are calculated for some final states of S and P symmetry by using the First Born Approximation and the Random Phase Approximation. The results for the total cross sections compare reasonably well with previous accurate values in the case of singlet-singlet transitions.     

Program of measurement of the asymmetry P at the minima of the differential cross section for elastic π + p scattering

A program of measurement of the polarization parameter P in elastic π ⁺ p interaction in the resonance region of backward pion scattering is presented. This program is aimed at determining the bifurcation points of the trajectory of zeros of the pion-nucleon amplitude and, hence, at unambiguously reconstructing the amplitude of πN scattering in the second resonance region. It is planned to perform a relevant experiment in a pion beam from the accelerator of the Institute of Experimental and Theoretical Physics (ITEP, Moscow).