F原子光电离截面的理论计算

对F原子的光电离截面,人们已经做了大量实验研究,并观察到了大量的自电离共振结构.而与实验相比,理论计算仍存在一定的差异.本文通过对靶态的能量进行修正,利用R矩阵方法计算了F原子基态在3P-1D电离阈值能量范围内的分波光电离截面、总光电离截面以及自电离共振2P4(1D)ns2D,2P4(1D)md2P和2P4(1D)md2D系列的共振位置,并与最新的多组态Hartree-Fock理论计算及实验结果进行了比较,我们的结果与实验符合得更好.     

N原子光电离截面的理论计算

利用R-矩阵方法计算了N原子基态在光子能量为1-3Ry范围内的光电离截面,给出了自电离态2s2p3(5S'0)np4P(n=3～10)的共振能量,我们的结果与已有的多组态Hartree-Fock理论计算(MCHF)及最近的实验结果相比符合得很好.     

钠蒸气中的双光子共振三光子电离和双光子混合共振三光子电离

在钠原子－分子混合样品中，分别运用双光子共振三光子电离以及双光子混合共振三光子电离，测得了钠原子４Ｄ态的电离流时间衰减曲线。由电离流与多光子动力学参数的关系，得到了４Ｄ态的光电离截面。     

钠蒸气中的双光子共振三光子电离和双光子混合并振三光子电离

在钠原子－分子混合样品中，分别运用双光子共振三光子电离以及双光子混合共振三光子电离，测得了钠原子４Ｄ态的电离流时间衰减曲线。由电离流与多光子动力学参数的关系，得到了４Ｄ态的光电离截面。     

类硼离子N2+光电离的R-矩阵理论计算

本文首次运用R-矩阵理论方法,分别在单通道近似和三态密耦近似下计算了离子N2+基态(1s22s22p) 2P的不同过程、不同分波的光电离截面及各分波的光电离截面随有效量子数的变化规律.在三态密耦近似下,由于大量的自电离态与连续态的相互作用,计算结果显示了光电离过程中非常丰富的Rydberg系列共振结构,是以前的理论计算中所从未涉及到的.     

钾原子的双光子共振三光子电离

在钾蒸气中用双光子共振三光子电离法测出了钾原子６Ｓ态的电离流随时间的衰减曲线。由电离流和多光子动力学参数的关系计算了６Ｓ态的光电离截面。当用７６６．４ｎｍ和７６９．８ｎｍ单光子激发时,通过能量积聚效应也可诱导钾原子得以电离。     

Sm原子奇宇称Rydberg态光谱

结合共振激发和场电离探测技术,通过总角动量量子数0→1→0→1的激发路径,研究了第一电离阈附近的Sm原子奇宇称Rydberg态4f~66snp(J=1)。首先,在45 200～45 500 cm~(-1)能量范围内共发现了94个奇宇称Rydberg能级。其次,通过对有效量子数和Rydberg能级结构特点的分析,将其中68个能级归属为3个束缚Rydberg系列,另外26个能级也给出了能级位置。然后,利用Rydberg-Ritz公式,对3个Rydberg系列分别进行了拟合,获得了Sm原子的电离阈为(45 519.61±0.79) cm~(-1)。最后,采用6种偏振组合激发,由偏振选择定则,进一步验证了这些奇宇称Rydberg态总角动量量子数为1。这些结果首次证实了场电离探测技术对Sm原子高激发Rydberg态的适用性,并且通过对奇宇称Rydberg系列拟合得到的Sm原子电离阈与文献中通过偶宇称Rydberg系列获得的值(45 519.64±1.39) cm~(-1)基本一致。     

用共振激发延迟电离方法测定原子激发态的光电离截面

用两束脉冲激光,一束使原子共振激发,另一束使激发态原子电离,当电离光脉冲能量约达1J/cm~2时,可使电离饱和.测量被电离原子数的相对大小与电离光脉冲能量之间的函数关系,可以方便地得出原子激发态的光电离截面.延迟电离光至激发光脉冲结束后到达作用区,可以修正激发光对电离的贡献,并避免电离光引起的Stark位移对共振激发的影响.应用共振激发延迟电离方法测定了Cs原子7~2P_(3/2)态的光(λ=5320(?))电离截面,测量值σ_I=6.5×10~(-18)cm~2与Manson的计算值非常接近.     

Eu原子4f~76snlRydberg态的研究

利用三步双色共振激发技术和三步三色孤立实激发技术,系统地研究了铕原子在42250—44510 cm~(-1)能域内的光谱特性,提供了该能域内56个束缚高激发态的光谱信息.为了能确定这些态的光谱归属,进行了两方面的探索:第一,观察能否利用孤立实激发技术,把处于这些态上的铕原子进一步共振激发到自电离态,从而推断这些态属于单电子激发的束缚Rydberg态还是属于双电子激发的价态,并对Rydberg态的电子组态进行了光谱确认;第二,通过计算这些态相对于各个电离阈的量子亏损并观察它们分别收敛于哪个电离阈,以便获取其主量子数的信息.最后,设计并采用了三种不同的激发路径,分别将原子布居到同一高激发能域并探测它们在该能域的光电离光谱.通过比较这些光谱的异同并结合上述激发路径所对应的跃迁选择定则,便可惟一地确定这些高激发态的总角动量.研究发现:所探测到的高激发束缚态只有三个属于单电子激发的束缚Rydberg态,其余都是价态.本文确定了这三个Rydberg态的电子组态和原子状态.     

类锂离子C3+激发态(1s22p)2P光电离的计算

文中首次运用R-矩阵方法,在三态密耦近似下计算了类锂离子C3+激发态(1s22p)2P光电离截面,主要给出了不同过程和不同分波的光电离截面.计算结果显示了光电离过程中非常丰富的Rydberg系列共振结构.     

He原子与HI分子碰撞截面的密耦计算

基于发展的分子间相互作用势, 采用密耦方法计算了入射能量从1到140?meV范围内He原子与HI分子碰撞的微分截面、分波截面和积分截面.通过与He-HX（X=F,Cl,Br）体系分波截面的比较, 印证了He-HI体系相互作用势以及密耦计算结果的可靠性.结果表明：小角散射的概率大于大角散射的概率;碰撞能量越高,散射概率就越小, 尾部效应也越弱.总积分截面主要来自弹性碰撞的贡献;非弹性积分截面以00→01和00→02跃迁的贡献为主,其中00→02跃迁的贡献最大. 关键词： 碰撞截面 密耦计算 HI-He体系     

Core-excited resonance enhancement in the two-photon complete fragmentation of helium

A time-dependent close-coupling method is used to calculate, for the first time, fully differential cross sections for the complete fragmentation of helium by two photons. Surprising differences in the magnitude of the total-integral cross sections are found in comparisons with other calculations. These differences are found to be due to a core-excited resonance enhancement of the two-photon process for both single and double ionization. These calculations provide theoretical support for ground-breaking measurements expected to be obtained from free-electron laser experiments in the near future.     

Elastic electron scattering with CH2Br2 and CCl2Br2: The role of the polarization effects

We present elastic electron scattering cross sections with holmethane molecules CH₂Br₂ and CCl₂Br₂ in the low-energy region ranging from 0.01 eV to 20 eV. The calculations are performed with the R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We find that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.     

Resonances in electron-impact integral excitation cross sections of the magnesium atom

The resonance structure of the integral cross sections of excitation of the magnesium atom by low-energy electrons is analyzed in terms of the R-matrix method. The collision strengths are calculated in terms of the close-coupling approximation with consideration of 25 atomic states, including 13 physical target states and 12 pseudostates. The latter simulate the remaining bound and continuum states of the Mg atom that were not included in the close-coupling expansion explicitly. The positions and widths of the resonances found are determined, and the resonances are classified with respect to the mechanism of formation of short-lived states of the negative Mg ion. The results of calculations are compared with available experimental data.     

Single electron loss in the collisions of C3 + and atomic hydrogen

This paper studies the projectile electron loss cross sections of C3+ colliding with atomic hydrogen in the frame work of extended over-barrier model at intermediate velocities (25 keV/u-600 keV/u). The electron loss is calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between projectile electron and target electron. Compared with the convergent close-coupling calculations, screening and anti-screening calculations, this model satisfactorily reproduces the experimentally obtained energy dependence of the electron-impact ionisation cross sections and the single electron loss cross sections over the energy range investigated here.     

Nonradiative charge transfer in collisions of protons with rubidium atoms

The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10 3 keV-10 keV.The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region.The importance of rotational coupling for chargetransfer process is stressed.Compared with the radiative charge-transfer process,nonradiative charge transfer is a dominant mechanism at energies above 15 eV.The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail.The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.     

Triple differential cross sections for the double photoionization of H2

Triple differential cross sections arising from the break up of the H2 molecule by a single photon are presented. The time-dependent close-coupling technique is used to calculate differential cross sections for various geometries. Excellent agreement is found between current work and recent exterior complex-scaling calculations, confirming, for the first time, the absolute magnitude of the triple differential cross sections. Our calculations also compare favorably with recent synchrotron light source measurements.     

The Coulomb capture of negative muons by hydrogen atoms in the non-adiabatic close-coupling approximation

We present some results obtained within the non-adiabatic close-coupling approximation for Coulomb capture during collisions of slow negative muons with hydrogen atoms. The calculations are performed in momentum-space and a statistical distribution analysis is used to obtain the final cross sections. The present model results are in harmony with existing calculations. We conclude that further calculations within the present approach are justified.     

Electron excitation processes in low energy collisions of hydrogen-helium atoms

The electron excitation processes of $\rm H(1s) + He(1s^{2}) \to H(2s/2p) + He(1s^{2})$ are studied in impact energy range of 20—2000 eV/u by using the quantum-mechanical molecular orbital close-coupling (QMOCC) method. Total and state-selective cross sections have been obtained and compared with the available theoretical and experimental results. The results agree well with available measurements in the overlapping energy regions overall. The comparison of our results with other theoretical calculations further demonstrates the importance of considering a sufficient number of channels. The datasets presented in this paper, including the excitation cross sections, are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00083.     

基于Ne-HBr从头算CCSD(T)势的散射截面

利用非线性最小二乘法拟合在CCSD(T)/aug-cc-pVQZ理论水平下计算的相互作用能,得到了基态Ne-HBr复合物相互作用势的解析表达式.基于拟合的从头算CCSD(T)势,通过收敛的密耦计算得到了入射能量分别为40,60,80和100 meV时,Ne-HBr散射的微分截面和分波截面,详细讨论了态-态转动激发截面对总非弹性散射截面的影响和散射截面随能量的变化趋势.希望研究结果对该体系的散射实验和进一步的理论研究能提供参考信息.