Compton profiles of electron momentum distribution inβ-Ga

We report for the first time the Compton profiles of electron momentum distribution inβ-gallium calculated along the crystallographic directions (100), (110) and (111). The conduction electron states for this purpose are determined in the energy band calculations using model potential. The core states, on the other hand, are represented each by a single tight-binding function. The results show that the Compton profiles are nearly isotropic with very little directional dependence, which is suggestive of a free-electron-like distribution of the conduction electrons in this system. The latter conclusion is in close confirmity with similar conclusions drawn in augmented plane wave (APW) calculation of energy bands and the derived Knight-shift results inβ-Ga.     

Electron momentum density distribution in iridium by Compton scattering technique

The isotropic Compton profile of iridium, measured using 59.54 keVγ-rays, is reported in this paper. The results are compared with the theoretical Compton profiles from APW method with and without incorporating electron correlation effects. It is seen that correlation effects improve the agreement between the experiment and theory. Comparison with the renormalized-free-atom (RFA) model calculations has also been made. Behaviour ofd-band electrons in Ir and some other 5d transition metals is discussed in terms of broadening in their Compton profiles.     

Compton profile of molybdenum

In this paper we report the experimental Compton profile of polycrystalline molybdenum. The measurements have been made by scattering 59.54 keVγ-rays and are compared with the recent band structure calculation of Janiet al. [4]. These results have also been compared with our calculation based on the renormalized-free-atom model for different 4d-5s configurations. It is found that the present experimental data are relatively in good agreement with the band structure calculation.     

Compton profile study of α-manganese

The results of a Compton profile study on polycrystallineα-Mn are reported. Our measurement are compared with theoretical results computed for different 3d-4s electron configurations within the RFA model. Best agreement between the measured and calculated values is found for 3d ^5·44s ^1·6 configuration. Theoretical Compton profile ofγ-Mn calculated using the same procedure is close to that for bcc phase with similar electron configurations.     

Experimental and theoretical Compton profiles of Be, C and Al

The results of Compton profile measurements, Fermi momentum determinations, and theoretical values obtained from a linear combination of Slater-type orbital (STO) for core electrons in beryllium; carbon and aluminium are presented. In addition, a Thomas-Fermi model is used to estimate the contribution of valence electrons to the Compton profile. Measurements were performed using monoenergetic photons of 59.54 keV provided by a low-intensity Am-241 γ-ray source. Scattered photons were detected at 90° from the beam direction using a p-type coaxial high-purity germanium detector (HPGe). The experimental results are in good agreement with theoretical calculations.     

Renormalized-free-atom model and Compton profile of hcp cobalt

Compton profile of cobalt has been calculated employing the renormalized-free-atom model for fcc as well as hcp phases choosing several 3d-4s configurations. The results have been compared with recent gamma-ray measurements on polycrystalline Co. Best agreement between theory and experiment is found for 3d ⁷4s ² configuration. Comparison with free electron model has also been made for this case.     

类氢离子的相对论康普顿轮廓（英文）

基于中心场近似得到Dirac径向轨道,并使用恰当的Fourier变换系统计算了类氢离子电子动量分布和康普顿轮廓。以H原子和Xe53+离子为例,探讨了相对论效应和原子核的有限体积效应对单电子康普顿轮廓的影响。同时,详细研究了单电子康普顿轮廓对主量子数n、轨道量子数l、单电子总角动量量子数j和核电荷数Z的依赖关系。结果表明,相对论效应可以扩展康普顿轮廓的分布,并且使给定nl的轨道随着Z的增加分裂得越来越明显。然而,相对论效应也会随着主量子数n和轨道量子数l的增加而减弱。同时,对于nl_j轨道,其康普顿轮廓还具有n-l个平台的结构。另外,原子核的有限体积几乎不会影响H原子和Xe53+离子的康普顿轮廓。The Compton profiles of the electron in the ground and excited states of H-like ions have been calculated systematically with one-electron Dirac radial orbitals by using the proper Fourier transformation. Taking the H atom and Xe53+ ion as examples, the effects of relativity and finite nuclear size on Compton profile have been discussed. Furthermore, the dependence of one-electron Compton profile on the principle quantum number n, orbital quantum number l, angular quantum number j and nuclear charge Z has also been discussed. It is found that the relativistic effect can expand the distribution of the Compton profile and split the orbital more and more obviously for given nl(l=0) as increasing Z. However, the relativistic effect can gradually weaken with the increase of the principal quantum number n and orbital quantum number l. Furthermore, the Compton profile of the orbital with quantum number nl_j has certain number of platforms that is n-l. In addition, the nuclear finite size hardly affects the Compton profile for H atom and Xe53+ ion.     

NO与C2H2的康普顿轮廓研究

基于第三代同步辐射光源, 在20 keV的入射X射线能量下测量了NO与C₂H₂分子的康普顿轮廓. 考虑到本次实验结果在p_z ≈ 0附近的统计精度达到了0.2%, 本文报道的NO和C₂H₂的康普顿轮廓可以作为严格检验理论的实验基准. 除此之外, 还分别采用HF方法及密度泛函方法选用不同的基组计算了NO 与C₂H₂康普顿轮廓. 通过对比实验结果与理论计算, 发现对于NO分子, 加入弥散函数基组理论计算结果与实验符合更好, 说明NO分子基态的电子分布较为弥散. 对于C₂H₂分子, HF方法理论计算的结果与实验符合较好.     

Room temperature Compton profiles of conduction electrons in α-Ga metal

Room temperature Compton profiles of momentum distribution of conduction electrons in α -Ga metal are calculated in band model. For this purpose, the conduction electron wave functions are determined in a temperature-dependent non-local model potential. The profiles calculated along the crystallographic directions, (100), (010), and (001) are found to be nearly isotropic. This conclusion is in reasonable agreement with experimental observations     

水分子在氢化锂表面的吸附行为

运用理论分析方法计算研究了水分子在氢化锂表面的吸附行为,分析了氢化锂表面改性对其疏水性能的影响。结果表明,在LiH-111面和LiH-100面上构建槽结构、柱状结构后,水分子在其上的吸附力比完整表面更强,说明表面微结构的引入的确改变了势能分布。壁相交处存在势能叠加,加强了吸附水分子的能力,但是没有引起表面的亲水性能变化。水分子可以稳定的吸附在完美的LiH（001）表面,其解离能垒仅为0.386 eV,这一解离反应在室温下完全可以进行。水分子极易在具有结构缺陷的LiH表面解离,这是LiH在一定湿度的空气和水环境中极易分解的根本原因。     

Performance of 20 Ci137Cs γ-ray Compton spectrometer for the study of momentum densities

In this paper, we present the design and construction of a 20 Ci γ-ray Compton spectrometer that employs a¹³⁷ Cs source with a strong line at 661.65 keV. The total resolution of the spectrometer in momentum scale is 0.40 a.u., which is much better than the conventional²⁴¹Am Compton spectrometers. The in-house¹³⁷Cs spectrometer is very useful for the measurement of momentum densities of heavy materials. The performance of the machine is assessed using aluminum, terbium and mercury samples and the experimental data from comparable apparatus.     

Electron momentum distributions and compton profiles of some molecules with FSGO model

The electron momentum distributions and the Compton profiles (within the impulse approximation) of H₂, LiH, methane, water, acetylene, ethylene, ethane cyclopropane and cyclobutane have been calculated using the floating spherical Gaussian orbital (FSGO) wavefunctions. The agreement of the single-FSGO Compton profiles with the corresponding experimental or the Hartree-Fock (HF-SCF) theoretical ones is fairly good in most of the cases examined. The advantages and drawbacks of using the FSGO model for the calculation of Compton profiles are discussed.     

Electronic structure of hafnium: A compton profile study

In this paper, we report the first-ever isotropic Compton profile of hafnium measured at an intermediate resolution, with 661.65 keV γ-radiation. To compare our experimental data, the theoretical computations have also been carried out within the framework of pseudopotential using CRYSTAL03 code and the renormalized-free-atom (RFA) model. It is found that the present experimental profile is in better agreement with the RFA calculations if the outer electronic configuration is chosen as 5d^3.26s^0.8. The cohesive energy of Hf is also deduced from the experimental data and is compared with the available data. On leave from Hindu College, Sonepat 131 001, India     

Growth and decomposition of lithium and lithium hydride on nickel

In this paper we have investigated the deposition, structure and decomposition of lithium and lithium-hydride films on a nickel substrate. Using surface sensitive techniques it was possible to quantify the deposited Li amount, and to optimize the deposition procedure for synthesizing lithium-hydride films.By only making thin films of LiH it is possible to study the stability of these hydride layers and compare it directly with the stability of pure Li without having any transport phenomena or adsorbed oxygen to obscure the results. The desorption of metallic lithium takes place at a lower temperature than the decomposition of the lithium-hydride, confirming the high stability and sintering problems of lithium-hydride making the storage potential a challenge.     

Strong anisotropy in the low temperature Compton profiles of electron momentum distribution in α-Ga metal

Compton profiles of momentum distribution of conduction electrons in the orthorhombic phase of α-Ga metal at low temperature are calculated in the band model for the three crystallographic directions (100), (010), and (001). Unlike the results at room temperature, previously reported by Lengeler, Lasser and Mair, the present results show strong anisotropy in the Compton profiles with the momentum distribution along (001) direction being substantially different from the other two directions. While experimental data on Compton profiles at low temperatures are not available for comparison with theory, the resistivity data in α-Ga at low temperature strongly support this anisotropic behaviour. Besides, the electronic heat capacity constant γ available from both experiment and present calculation suggests that the conduction electron distribution at low temperature in the orthorhombic phase is markedly different from the free-electron-like-distribution at room temperature, thus lending additional support to anisotropic behaviour of Compton profiles. It would be nice to have Compton profiles data from experiment at low temperature for direct comparison with theory. It is hoped that the present work would stimulate enough interest in that direction.     

激光等离子体中多光子非线性Compton散射的光子加速

利用相对论性电子与光子非弹性碰撞模型，研究了激光等离子体中发生多光子非线性Gompton散射时，由于尾波场的作用而引起的散射光子频率的变化。结果表明，光子可以从激光场中获得能量，在光子总数减少的情况下，光子频率增大，光子获得加速。     

Theoretical calculation for the equation of state and phase transition of lithium hydride crystal

Abstract

From the point of view of overlapping interactions between the nearest neighbours, while considering the compression effect of each ion, an ionic overlap-compression model is founded and applied to lithium hydride. The repulsive potential and cohesive energy curves of the crystal are calculated by a one-parameter variational method. The obtained equilibrium lattice constant (3.865 a₀), cohesive energy (? 218.82 kcal/mol), and bulk modulus (353 kbar) agree with experimental values surprisingly well. The calculated values of the equation of state also reach a good agreement with the experimental ones available below 40 kbar. A phase transition from NaCl to CsCl structure is predicted to occur around 0.85 Mbar, with a volume jump of about 6%.     

A compton profile study of tantalum

We report the results of Compton profile study on polycrystalline tantalum. Measurements have been made using 59.54 keV gamma-rays. The results are compared with the APW band structure calculations of Papanicolaouet al and other available data. In contrast to the work of Changet al the overall agreement is better with the APW band structure which worsens on incorporating the electron correlation correction. Estimates of the errors due to the contribution from bremsstrahlung, non-validity of impulse-approximation and anomalous dispersion are also briefly discussed.     

Compton散射下超强激光等离子体通道的演化

应用多光子非线性Compton散射模型、空间动态补偿模型、非线性薛定谔方程和数值模拟方法,研究了Compton散射对超强飞秒激光等离子体中通道的影响,提出了将Compton散射光作为形成等离子体通道的新机制,给出了超强飞秒激光脉冲在等离子体中传播和电子密度随时间变化的非线性修正方程,并进行了数值模拟.研究发现:散射使等离子体中电子密度峰值增大1个量级,半径增大1 mm.激光最大功率密度被限制在10~(18)W/m~2以下,随传输距离增大缓慢衰减.传输初始阶段,单脉冲衰减能量较散射前增大2%,之后衰减较平缓.通过增加超强飞秒激光脉冲输入功率,能有效地增加电子密度峰值,有利于等离子体通道的形成.并对所的结论给出了初步物理解释.     

Compton散射下超强激光等离子体通道的演化

应用多光子非线性Compton散射模型、空间动态补偿模型、非线性薛定谔方程和数值模拟方法,研究了Compton散射对超强飞秒激光等离子体中通道的影响,提出了将Compton散射光作为形成等离子体通道的新机制,给出了超强飞秒激光脉冲在等离子体中传播和电子密度随时间变化的非线性修正方程,并进行了数值模拟。并研究发现：散射使等离子体中电子密度峰值增大1个量级,半径增大1mm。激光最大功率密度被限制在1018W/m2以下,随传输距离增大缓慢衰减。传输初始阶段,单脉冲衰减能量较散射前增大2%,之后衰减较平缓。通过增加超强飞秒激光脉冲输入功率,能有效地增加电子密度峰值,有利于等离子体通道的形成。并对所的结论给出了初步物理解释。