Absolute double differential ionization cross-section for electron impact: He

Summary A complete set of absolute double differential cross-section (DDCS) for electron impact ionization of helium has been measured at an incident energyE ₀=500 eV. The angular distributions of the ejected and scattered electrons between 40 and 435.5 eV have been measured over the angular range of (10÷145)^o. This work supplements the mapping of DDCS for ejected electron energies close to (E ₀−IP)/2 (IP is the He 1s ionization energy), a region where the experimental data are fragmentary. The possibility of representing the full Bethe surface with a simple functional form is investigated. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

电子与钠原子散射的S, T, U参数研究

电子原子散射中的S，T，U参数可用来描述散射前后自旋状态的变化，研究精细结构水平上的散射激发振幅之间的关系，进而揭示电子原子碰撞过程中电子自旋-轨道耦合以及电子-电子交换等自旋相关效应.采用扭曲波玻恩近似计算了钠原子受电子散射S→P跃迁中的S，T，U参数，分析了多种入射能(2.2—60 eV)的电子与钠原子激发S→P跃迁过程的S,T,U参数随散射角的分布，其中对10 eV入射能的S_p参数与已报道实验数据符合一致.结果表明，较低能电子入射下的S,T,U参数随散射角的分布幅度和起伏都比较明显，入射能大于40 eV的电子入射，S,T,U参数的散射角分布变化很小. 关键词： 散射激发 S')" href="#">S T')" href="#">T U参数')" href="#">U参数 散射振幅 自旋相关效应     

Scattering of electrons with formyl radical

A detailed theoretical study is carried out for electron interactions with formyl radical (HCO) with incident energies ranging from 0.01 to 5000 eV. This wide range of energy has allowed us to investigate a variety of processes and report data on vertical electronic excitation energies, dissociative electron attachment (DEA) and total cross-section along with scattering rate coefficients. We observed Ramsaur–Townsend minimum at 0.59 and 0.74 eV using DZP and cc-pDVZ basis sets, respectively. HCO has large number of low-lying excited states and the present study finds an overall good agreement with earlier reported data. In order to compute total cross-section, we have employed ab initio R-matrix method (0.01 to ～ 20 eV) and the spherical complex optical potential method (～ 10 to 5000 eV) employing static-exchange plus polarisation potential. The R-matrix calculations are performed using a close coupling method with the aid of 21 target states, 1191 configuration state functions and 195 channels. The DEA cross-sections of fragmentation of H^?, excitation cross- sections and scattering rate coefficients are reported for the first time. Total cross section presented here will provide a reference data set over an extensive impact energy range.     

Modifications in high energy higher order Born approximation

A systematic study is made to find out the differential scattering cross-section in the case of electron-atom collisions. The first and the second Born terms ofO(1/k _i ) are calculated in the framework of Yates high energy higher order Born approximation. The second Born term ofO(1/k _i ² ) is calculated using the second order Wallace term, the third term is calculated using the Glauber-eikonal series of Yates. The method is applied to the elastic scattering of electrons by atomic hydrogen in the energy range 100–400 eV and by helium for energies 200 eV and 400 eV. Comparison is made with other theoretical results and the experimental data.     

Resonances in the dtµ molecular ion between tµ(n=2) and dµ(n=2) thresholds

Elastic and inelastic cross sections in collisions of a tµ atom in 2s and 2p states on deuteron have been obtained within the framework of a four-channel adiabatic approximation for the case of total orbital angular momentumJ=0. The calculated data has been applied to verify the existence of resonance in the dtµ molecular ion at 0.8 eV above the tµ(n=2) threshold. It appears that the second and third resonant states (at 0.8 eV and at 7 eV above the tµ threshold) in a series converging to the dµ(n=2) threshold do not produce any resonant structure in the energy spectrum. The higher vibrational states are visible in the spectrum, however their widths are about 0.1 eV and therefore their life-times are about 10^–15 s which allows to conclude that these states could not play an important role in the µCF cycle as well as in processes of diffusion of muonic atoms.     

XF3 (X=N,P,As)价层电离势的运动方程耦合团簇理论计算

采用运动方程单双取代耦合团簇理论(EOM-CCSD)对XF₃(X=N,P,As)的价层垂直离势(VIP)进行了系统计算,同时对称匹配团簇组态相互作用(SAC-CI)、外价层格林函数(OVGF)以及部分三阶近似(P3)方法也被应用到目前计算.与已有的实验结果比较表明:EOM-CCSD计算的价层垂直电离势整体上与SAC-CI结果相近,而优于OVGF和P3理论结果,在整个价层上,EOM-CCSD结果与实验值总体差距约0.2 eV, 在外价层这种差距相对较小,在内 关键词： XF₃(X=N;P;As)')" href="#">XF₃(X=N;P;As) 垂直电离势 运动方程耦合团簇理论     

Comparison of eikonal-Born series and modified Gluaber approach for the study of elastic electron-hydrogen scattering

Elastic electron-hydrogen scattering at medium and high energies has been analysed in eikonal-Born series and modified Glauber approach forE _i ≥ 50 eV. We have used closed form expressions for evaluating the second Born term in the fixed scatterer approximation and for higher order terms of Glauber-eikonal series. The exchange effect has also been included via Glauber-Bonham-Ochkur type procedure. The fixed scatterer approximation calculations are compared with results obtained using other approximations for the second Born term available in the literature. The results compare fairly well with experimental data.     

Spin polarization of electrons elastically scattered from europium and bismuth atoms

We present calculations of differential, integrated elastic, total, momentum transfer cross-sections and spin-polarization parameters S, T and U for scattering of electrons from Eu and Bi atoms in the energy range 2.0 to 500.0 eV using semi-relativistic approach. The target-projectile interaction is represented both by real and complex parameter-free optical potentials in the solution of Dirac equation for the scattered electrons. The results for the differential cross-sections and spin-polarization parameters have been compared with the available calculations and experimental results. Received 17 February 2000 and Received in final form 15 June 2000     

Studies on differential cross-sections of e–N2 scattering

The differential cross-sections (DCS) of the low-energy electron–N ₂ scattering are studied using the vibrational close-coupling (VCC) method and vibrational scattering potentials which include static, exchange and polarization contributions. The polarization is obtained based on the ‘better than adiabatic dipole’ (BTAD) and the ‘distributed spherical Gaussian’ (DSG) respectively. The converged (0 → 0, 0 → 1, 0 → 2, 0 → 3) DCS are obtained with the impact energies being the resonance's first two elastic scattering peaks?–?approximately 1.90 eV and 2.10 eV. Calculations from both polarization potentials agree with experimental results.     

Electronic structures and mechanical properties of uranium monocarbide from first-principles and calculations

The electronic structure, elastic constants, Poisson's ratio, and phonon dispersion curves of UC have been systematically investigated from the first-principles calculations by the projector-augmented-wave (PAW) method. In order to describe precisely the strong on-site Coulomb repulsion among the localized U 5f electrons, we adopt the local density approximation (LDA)+U and generalized gradient approximation (GGA)+U formalisms for the exchange correlation term. We systematically study how the electronic properties and elastic constants of UC are affected by the different choice of U as well as the exchange-correlation potential. We show that by choosing an appropriate Hubbard U parameter within the GGA+U approach, most of our calculated results are in good agreement with the experimental data. Therefore, the results obtained by the GGA+U with effective Hubbard parameter U chosen around 3 eV for UC are considered to be reasonable.     

Elastic scattering ofα-particles from20Ne

A relatively simple procedure using nuclear interaction calculated microscopically from two-nucleon potential employing equivalence of resonating group method and generator coordinate method has been used to calculate the differential cross-sections (DCS) forα +²⁰Ne elastic scattering atE _lab=18.0, 20.2, 21.9, 23.0 and 27.2 MeV. The absorption effects due to the opening of the non-elastic channels are taken into account approximately by the sharp cut-off of lower partial waves. The anomalous large oscillations of the DCS at backward angles atE _lab=18.0 and 27.2 MeV are reproduced. The calculated results are in fair agreement with the experimental data.     

Ramsauer–Townsend Effect in Solid Hydrogen

The TRIUMF E742 experiment has measured the energy dependence of the scattering cross-sections of muonic deuterium and tritium on hydrogen molecules for collisions in the energy range 0.1–45 eV. The experimental setup permits the creation of muonic atom (μd or μt) beams. The multilayered target system gives the possibility to choose the type of interactions to study and to isolate a particular interaction. The scattering of μd or μt beams on H₂ is analyzed via the muon transfer reaction to neon. The time-of-flight method is used to measure the scattering cross section as a function of the energy of the muonic atom beam. The results are compared, using Monte Carlo simulations, with theoretical calculations which have been recently performed with high accuracy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Elastic scattering of electrons from oxygen and ozone molecules at high energies

Elastic differential cross-sections for thee-O₂ ande-O₃ systems are obtained in the independent atom model at high energies (E _i ⩾ 300 eV). The basic atomic scattering amplitudes are obtained in the partial wave method through a sum of static exchange and polarization potentials. Oure-O₂ results agree with experiments except for small angles. No data are available for O₃, for comparison.     

Cross sections and other parameters ofe − − H2O scattering (E i⩾50 eV)

Our previous theoretical work one ⁻ − H₂O scattering has been modified and extended to intermediate and high energiesE _i. Using the Bethe plot, we compare the present inelastic cross-sections with the experimental ionization cross sections. Total cross-sections are analytically represented asQ _TOT(cm²)=a.(E _ieV) ^−b and the parameters ‘a’ and ‘b’ are discussed for molecules H₂O, NH₃ and CH₄ in the rangeE _i=100–1000eV.     

Dispersive optical constants of a-Se100−xSbx films

Thin films of amorphous Se_100−xSb_x (x=5,10 and 20 at%) system are deposited on a silicon substrate at room temperature (300 K) by thermal evaporation technique. The optical constant such as refractive index (n) has been determined by a method based on the envelope curves of the optical transmission spectrum at normal incidence by a Swanpoel method. The oscillator energy (E_o), dispersion energy (E_d) and other parameters have been determined by the Wemple–DiDomenico method. The absorption coefficient (α) has been determined from the reflectivity and transmitivity spectrum in the range 300–2500 nm. The optical-absorption data indicate that the absorption mechanism is a non-direct transition. We found that the optical band gap, E_g^opt, decreases from 1.66±0.01 to 1.35±0.01 eV with increase Sb content.     

Multicomponent Rayleigh scattering from guanidine hydrochloride solutions

We present results of Brillouin light scattering studies of lysozyme and guanidine hydrochloride solutions in the temperature range 290–350 K. The Brillouin spectra of 6 M guanidine hydrochloride have been found to contain an additional component in Rayleigh scattering that manifests itself as a broad quasi‐elastic scattering line centered at the unshifted frequency and described by a Lorentz function (i.e. a Debye relaxor with relaxation time τ₁ ~ 25 ps at room temperature). The temperature dependence of τ₁ is described by the Arrhenius law with activation energy E_a = 0.11 ± 0.01 eV and prefactor τ₀= 0.33 ± 0.03 ps. The Brillouin spectra of lysozyme denatured by 6 M guanidine hydrochloride exhibit a more complicated structure of the additional contribution into Rayleigh scattering, which is fitted best of all by a sum of two Lorentzians centered at the unshifted frequency (with relaxation times τ₁ ~ 19 ps and τ₂ ~ 180 ps at 339 K). Possible origins of the quasi‐elastic scattering are discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Elastic scattering of e∓ by Na atoms

ABSTRACT

The differential, integrated elastic, momentum transfer, viscosity and total cross-sections along with Sherman function for the elastic scattering of electrons and positrons by sodium atoms have been calculated within the framework of complex projectile–atom optical potential model at the impact energies 0.1 ≤ E_i ≤ 10⁴ eV for both the projectiles. The relativistic Dirac partial wave techniques, with accurate analytical charge densities, are used to obtain the scattering amplitudes. The present results produce satisfactory agreement with the experimental measurements and other theoretical calculations available in the literature.     

An X‐ray Raman spectrometer for EXAFS studies on minerals: bent Laue spectrometer with 20 keV X‐rays

An X‐ray Raman spectrometer for studies of local structures in minerals is discussed. Contrary to widely adopted back‐scattering spectrometers using ≤10 keV X‐rays, a spectrometer utilizing ～20 keV X‐rays and a bent Laue analyzer is proposed. The 20 keV photons penetrate mineral samples much more deeply than 10 keV photons, so that high intensity is obtained owing to an enhancement of the scattering volume. Furthermore, a bent Laue analyzer provides a wide band‐pass and a high reflectivity, leading to a much enhanced integrated intensity. A prototype spectrometer has been constructed and performance tests carried out. The oxygen K‐edge in SiO₂ glass and crystal (α‐quartz) has been measured with energy resolutions of 4 eV (EXAFS mode) and 1.3 eV (XANES mode). Unlike methods previously adopted, it is proposed to determine the pre‐edge curve based on a theoretical Compton profile and a Monte Carlo multiple‐scattering simulation before extracting EXAFS features. It is shown that the obtained EXAFS features are reproduced fairly well by a cluster model with a minimal set of fitting parameters. The spectrometer and the data processing proposed here are readily applicable to high‐pressure studies.     

Neutron scattering from <Emphasis Type="Italic">α</Emphasis>-Ce at epithermal neutron energies

Neutron scattering data, using neutrons of incident energies as high as 2 eV, on α-Ce and α-Ce-like systems such as CeRh₂, CeNi₂, CeFe₂, CeRu₂, and many others that point clearly to the substantially localized 4f electronic state in these systems are reviewed. The present interpretation is contrary to the widely held view that the 4f electrons in these systems form a narrow itinerant electron 4f band.      

双层喷气Z箍缩氖等离子体K层辐射研究

报道了"强光一号"(1.6 MA,70 ns)加速器驱动双层喷Ne气Z箍缩负载产生K层辐射(光子能量约1 keV)的实验研究.喷气负载出口半径为1.5—1.4 cm和0.75—0.6 cm(半径比2 ∶1).充气压力相同情况下外层和内层质量比约2.8 ∶1.在内爆时间约120 ns、负载线质量估计值60—70 μg/cm时,获得K层辐射产额约7 kJ、峰值功率0.28 TW,脉冲宽度20 ns.X射线分幅图像表明内爆阶段的不稳定性影响较小,最终内爆速度超过25 cm/μs,等离 关键词： 双层喷气 Z箍缩等离子体 K层辐射')" href="#">K层辐射 雪耙内爆