共查询到20条相似文献,搜索用时 218 毫秒
1.
研究了高电荷态离子Arq+(q=16,17,18)入射金属Be,Al,Ni,Mo,Au靶表面产生的X射线谱.实验结果表明,Ar的Kα-X射线是离子在与固体表面相互作用过程中固体表面之下形成空心原子发射的.电子组态1s2的高电荷态Ar16+离子在金属表面中性化过程中,存在的多电子激发过程使Ar16+的K壳层电子激发产生空穴,级联退激发射Ar的Kα 特征X射线.Ar17+离子在金属表面作用过程中产生的X射线谱形与靶材料没有明显的关联,入射离子的Kα-X射线产额与其最初的电子组态有关,靶原子的X射线产额与入射离子的动能有关.
关键词:
高电荷态离子
空心原子
多电子激发
X射线 相似文献
2.
现代光源的发展不断推动着人们从更深层次上理解物质的基本结构和动力学行为。X射线自由电子激光作为最先进的光源,其超高的峰值功率、超短的脉冲长度和优良的相干性,为人们以原子级时空分辨率探测和操控物质中的超快过程提供了可能。目前全世界已有多个X射线自由电子激光装置建成并投入使用,在原子分子物理、化学、生命科学、材料科学等各学科应用中都显示出了重要价值。同时大量的研究工作也集中于继续提高X射线自由电子激光的性能,包括把脉冲持续时间从fs量级进一步缩短至as量级,这将为超快科学的发展带来新突破。以超快脉冲产生为主线,综述了近年来超快X射线自由电子激光产生方案的研究进展,从产生原理、方案特性、最新成果等方面介绍了各类产生方案,总结对比了各方案的优缺点,最后对超快X射线自由电子激光的未来发展方向进行了展望。 相似文献
3.
研究了高电荷态离子Arq+(q=16,17,18)入射金属Be,Al,Ni,Mo,Au靶表面产生的X射线谱.实验结果表明,Ar的Kα-X射线是离子在与固体表面相互作用过程中固体表面之下形成空心原子发射的.电子组态1s2的高电荷态Ar16+离子在金属表面中性化过程中,存在的多电子激发过程使Ar16+的K壳层电子激发产生空穴,级联退激发射Ar的Kα特征X射线.Ar17+离子在金属表面作用过程中产生的X射线谱形与靶材料没有明显的关联,入射离子的Kα-X射线产额与其最初的电子组态有关,靶原子的X射线产额与入射离子的动能有关. 相似文献
4.
美国科学家首次用红外光与X射线激光的组合,在原子尺度上研究光与物质的相互作用.这种技术是使用红外光和X射线照射同一个钻石样品.部分红外光被钻石的价电子吸收,其能量又转移给一些从样品散射出的X射线.由此,研究人员能够将与价电子相互作用的X射线和从样品原子的壳层内的电子散射的X射线区分开.X射线衍射技术是利用从物质原子周围的电子云散射的X射线,可以给出大量关于物质结构和成分的 相似文献
5.
考察了激发态之间的电离与复合过程对等离子体状态的影响,并对其原因进行了细致的分析,分别考察了对1.0ns,100ps和5ps激光驱动的类氖锗19.6nm X射线激光增益系数的影响.研究表明,对于5ps激光驱动的瞬态机理X射线激光来讲,因增益区处在高密度区,所以,激发态之间的电离与复合过程对X射线激光将不可以忽略.对于1.0ns和100ps激光驱动的亚稳态机理X射线激光来讲,在电子密度小于等于5×1020cm-3的区域,忽略激发态之间的电离与复合使增益的时间半高全
关键词:
X射线激光
矩阵分块法
类氖锗
双电子激发态 相似文献
6.
利用中国原子能科学研究院HI-13MV串列加速器上提供的动能为15—55 MeV的类氦C离子分别轰击Fe, Ni, Nb和Mo金属厚靶,采用HpGe探测器测量了K-X射线,获得了相应的K-X射线的发射截面.本文中由于各个靶原子外壳层电离度的不同,类氦C离子与Fe, Ni靶原子相互作用发射的Kβ与Kα X射线的分支强度比随入射离子动能增加而减小,而Nb, Mo靶原子发射的K-X射线分支强度比变化不明显.利用厚靶截面公式计算了靶原子K-X射线的发射截面,并与不同的理论模型及质子的结果进行了对比.结果表明随类氦C离子动能的增大, Fe, Ni靶原子发射的Kβ与Kα X射线的总产生截面与考虑多电离的两体碰撞近似修正模型最为符合Nb, Mo靶原子发射的Kβ与Kα X射线的总产生截面与平面波恩近似模型的理论值最为接近.质子与单核子C离子能量相同时,质子比类氦C离子激发不同靶的K-X射线产生截面约小3个数量级. 相似文献
7.
8.
《物理学报》2021,(19)
报道了 1.5—20 keV/q的高电荷态O~(q+)(q=3—7)离子与Al表面相互作用发射的O原子的特征X射线谱.分析表明,对于O~(q+)(q=3—6)离子入射时发射的X射线,是由于离子进入表面后与Al原子发生紧密碰撞导致的;而O~(7+)离子入射时的X射线,主要来自于"空心原子"的衰变.在动能相等的条件下,存在K壳层空穴的O~(7+)离子的X射线产额相较于O~(q+)(q=3—6)离子高一个数量级,不存在K壳层空穴的O~(6+)离子的X射线产额也要高于O~(3+),O~(5+)离子.总体来说,X射线产额以及电离截面与入射离子的初始电子组态有关,且随离子入射动能的增加而增加.根据半经典两体碰撞模型,本文估算了入射离子与靶原子相互作用时分别产生O和Al的K_α-X射线的动能阈值.对于入射动能低于动能阈值且电子组态为1s~2的O~(6+)离子与样品表面相互作用,可能存在多电子激发使O~(6+)离子产生K壳层空穴. 相似文献
9.
10.
11.
Interference effects on the photoionization cross sections between two neighbouring atoms: nitrogen as an example
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Interference effects on the photoionization cross sections
between two neighbouring atoms are considered based on the coherent
scattering of the ionized electrons by the two nuclei when their
separation is less than or comparable to the de Broglie wave length
of the ionized electrons. As an example, the single atomic nitrogen
ionization cross section and the total cross sections of two
nitrogen atoms with coherently added photoionization amplitudes are
calculated from the threshold to about 60~\AA (1~\AA=0.1~nm) of the
photon energy. The photoionization cross sections of atomic nitrogen
are obtained by using the close-coupling R-matrix method. In the
calculation 19 states are included. The ionization energy of the
atomic nitrogen and the photoionization cross sections agree well
with the experimental results. Based on the R-matrix results of
atomic nitrogen, the interference effects between two neighbouring
nitrogen atoms are obtained. It is shown that the interference
effects are considerable when electrons are ionized just above the
threshold, even for the separations between the two atoms are larger
than two times of the bond length of N2 molecules. Therefore, in
hot and dense samples, effects caused by the coherent interference
between the neighbours are expected to be observable for the total
photoionization cross sections. 相似文献
12.
The problem of ionization of ions in ion-ion and ion-neutral relativistic collisions is considered. Formulas for ionization
cross sections are derived in the Born approximation in terms of the momentum transfer without allowance for magnetic interactions.
Using these formulas implemented in the LOSS-R code, the ionization cross sections are calculated for the K shells of neutral atoms colliding with protons and also for 1s and 2p electrons of multiply charged heavy ions (nuclear charge Z = 80−90) colliding with bare nuclei and neutral atoms. The calculation results are compared with experimental data and calculations
of other authors. 相似文献
13.
Electron impact ionization cross sections of Ne, Ar, Kr, and Xe atoms are numerically calculated. The electron perturbation
in the continuous spectrum in the target field is taken into account. The matrix elements are calculated in many-electron,
nonrelativistic approximation with allowance for the superposition of configurations and relaxation effect. The radial part
of the electron wave function in the continuum is calculated by solving the single-configuration Hartree-Fock equation. The
wave functions of electrons in the continuum are orthogonalized with respect to the core orbital functions. The calculated
cross sections are compared to the experimental data and calculations made using the plane-wave Born approximation and that
involving generalized oscillator strengths. 相似文献
14.
N. V. Novikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(2):297-300
The cross section of ionization of atoms by protons is calculated in the plane-wave approximation. It is shown that the wave function of the ejected electron must be orthogonal to all wave functions of the atom. A method taking into account a finite number of wave functions in the calculation of the ionization amplitude is proposed. The calculated cross sections of ionization of nitrogen, oxygen, and neon atoms by protons agree well with the experimental data and results of calculations carried out by other authors. 相似文献
15.
V. I. Grebennikov T. V. Kuznetsova M. V. Yakushev 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(9):1123-1126
The electron structure of CuIn1 ? x Ga x Se2 single crystals is determined via resonant photoemis-sion and the main regularities of its transformation upon varying concentration x from 0 to 1 are established. The dependence of the shape of valence band spectra on the photon energy is studied. Integral photoemission intensities are shown to be determined by atomic photoionization cross sections. Processes of the direct and two-step creation of photoelectrons accompanying photoemission and the participation of internal states in the spectra of electrons from valence bands are studied. Two-hole final states in photoemission are obtained upon threshold excitation of the Cu 2p level. The strong interaction of holes leads to the multiplet splitting of these states. Partial densities of the components’ states are determined using the energy dependence of atomic photoionization cross sections. 相似文献
16.
基于多组态Dirac-Fock方法的程序包GRASP92和RATIP及在此基础上最新发展的RELPHOTO08程序, 系统地研究了高离化态金离子M壳层的光电离截面随入射光子能量、 离化度以及壳层的变化规律。结果表明: 光电离截面随光子能量的增大而单调减小; 电离nl电子时, 如果相关电子的主量子数较大, 则该电子存在与否对其光电离截面几乎没有影响; 在同一离化度下, 角量子数l可引起两种性质不同的效应, 其相互竞争可导致光电离截面随入射光子能量的复杂变化。Based on multiconfiguration Dirac Fock method and the corresponding packages GRASP92 and RATIP, as well as the newly developed RELPHOTO08, the variations of M subshell photoionization cross sections with the photon energy, ionization degree and subshells for highly charged gold ions are studied systemically. The present results show that the cross sections are decreasing monotonously with the photon energy; for the photoionization of nl electrons, if the principal quantum number of removed electron is large enough, the cross sections are essentially unchanged upon the presence or absence of outer electrons; for same ionization degree, the angular quantum number introduces two opposite effects which could exist simultaneously, and the intricate variations of cross sections with the photon energy originate from the competition between these two different effects. 相似文献
17.
18.
The cross sections of the photoionization and the electron impact-induced ionization of Yb atoms from the excited 6s6p(3
P
1) state are numerically calculated. Matrix elements are computed in multielectron relativistic and nonrelativistic approximations
with allowance for the superposition of configurations and a relaxation effect. The radial part of the electron wavefunction
in a continuous spectrum is calculated using the solutions to one-configuration Hartree-Fock and Dirac-Fock equations. The
cross sections calculated by a relativistic method are compared to those for a nonrelativistic approximation. The ratios of
the radiation reduced matrix elements and the phase shifts of the wavefunctions of a continuous spectrum calculated for the
6p ɛs and 6p → ɛd transitions are compared to the values obtained by approximating the experimental dependences of the angular distribution
of photoelectrons for the photoionization by ultraviolet radiation from an oriented excited state. 相似文献
19.
We present the first measurement of (e,2e) ionization cross sections for a laser oriented atomic target by spin polarized electrons. Cross sections are presented as a function of target orientation and polarization direction of the incident electron beam. This study provides insight into mechanisms by which angular momentum is transferred from the valence electron to the two final-state continuum electrons in both singlet and triplet spin channels, by comparing measurement with distorted wave Born approximation and the dynamically screened three Coulomb wave calculations. 相似文献