质子与羟基碰撞的含时密度泛函理论研究

采用将含时密度泛函理论和分子动力学非绝热耦合的方法,研究了不同入射速度下质子与羟基碰撞的反应动力学.计算了碰撞前后质子动能和羟基动能的变化及羟基电子和质子的运动.计算结果表明,质子沿垂直羟基分子轴方向入射时,质子与羟基碰撞后,质子被反弹且动能损失并俘获了羟基中氧的一部分电子,而丢失部分电子的羟基则获得动能以伸缩振动的形式向计算边界平动.随着入射质子的初动能增加,质子从羟基中俘获的电子增多,碰撞后羟基的键长变长,羟基振动变强而伸缩振动频率降低.此外,还发现质子的入射方向对碰撞过程的激发动力学有很大的影响.质子从不同的方向入射时,质子的入射初动能越大,其损失的动能越多且损失的动能与入射初动能呈线性关系,而入射方向对质子动能损失的影响很小.在质子入射初动能较低(小于25 eV)的情况下,羟基获得的动能与质子入射初动能呈线性关系且与入射方向无关;在质子入射初动能较高(大于25 eV)时,当质子沿羟基分子轴方向入射时,羟基动能的增量远大于质子沿垂直于羟基分子轴方向入射时羟基动能的增量.     

质子与乙烯分子碰撞的密度泛函理论研究(英文)

采用含时局域密度近似与分子动力学相结合的方法研究了不同入射速度的质子与乙烯分子碰撞的动力学。计算了质子的能量损失及碰撞后乙烯分子的电子和离子的运动状态, 研究了质子的入射方向及入射动能对整个系统的碰撞动力学的影响。计算结果表明, 当入射质子的动能较小（E_k0<250 eV）时, 在相同的入射速度下, 当质子垂直于分子平面入射时, 系统的电离最大, 质子俘获的电子多; 当质子的入射动能E_k0>250 eV时, 质子的能量损失与入射方向有密切的关系。In the framework of the time dependent local density approximation (TDLDA),which applied to valence electrons, coupled non adiabatically to molecular dynamics of ions, the microscopic mechanisms of collisions between energetic protons and ethylene are studied. Not only the amount of energy lost of the projectile, but also the electron and vibration excitations of the target are identified. In addition, the influences of the collision orientation on the energy loss of the proton and excitation dynamics of ethylene are discussed. It is found that the ionization is enhanced and more electrons are captured by the proton when the proton with the impact energy less than 250 eV moves perpendicularly to the molecular plane. A strong relation between the proton energy lost and the impact orientation is obtained when the impact energy is larger than 250 eV.     

电子与D2分子的相关量子动力学的理论研究

文章利用含时波包方法，通过求解三维电子与核运动相关的薛定谔方程得到了D^＋离子的动能分布，同时电子被电离后多次返回与D2^＋离子发生碰撞的儿率也得到了计算，并发现D^＋离子主要来源于电子与D2^＋离子在各个波长第一个光周期内的第一次碰撞，我们的计算结果不但与实验符合较好，而且给出了在阿秒时间分辨率下追踪电子与核相关运动的量子动力学方法。     

质子与Be原子的碰撞电离过程研究

本文采用初态程函近似一连续扭曲波方法研究了质子和Be原子的碰撞电离过程：计算了入射离子能量从50keV／u到10000keV／u时一阶和二阶微分散射截面随电离电子能量和角度的变化规律，并对各种碰撞电离机理进行了详细讨论；计算所得总截面随入射离子能量的变化规律也与已有数据一致；另外采用FAC代码研究了Be原子的内壳层电子（1s）被电离后的俄歇过程．     

类氢He+、Li2+离子的电子碰撞强度的R矩阵计算

利用R矩阵方法计算了电子与He+离子碰撞的1s-2s和1s-2p跃迁的碰撞强度,结果表明包括10个靶态的计算可以得到精确的类氢离子的n=1→n=2各能级跃迁的碰撞强度,并首次利用R矩阵方法计算了电子与Li2+离子碰撞的1s-2s和1s-2p跃迁的碰撞强度.     

Eu$lt;sup$gt;20+$lt;/sup$gt;入射Au靶发射Eu L-X射线产额与动能的相关性

探测了动能为3.0–6.0 MeV的Eu²⁰⁺离子入射Au靶激发Eu的L-X射线谱,获得了射线产额与离子入射动能的实验关系. 采用有心保守力作用下的两体碰撞模型,并考虑了离子的能损,计算了Eu离子与Au 原子碰撞过程中单离子L壳层空穴的产额. 根据离子L 壳层空穴退激的荧光产额,给出了碰撞过程Eu单离子L-X 射线产额与离子入射动能的理论关系. 结果表明,射线产额的理论值与实验数据符合得较好. 关键词： 离子动能 荧光产额 单离子X射线产额     

Eu~(20+)入射Au靶发射EuL-X射线产额与动能的相关性

探测了动能为3.0—6.0 MeV的Eu20+离子入射Au靶激发Eu的L-X射线谱,获得了射线产额与离子入射动能的实验关系.采用有心保守力作用下的两体碰撞模型,并考虑了离子的能损,计算了Eu离子与Au原子碰撞过程中单离子L壳层空穴的产额.根据离子L壳层空穴退激的荧光产额,给出了碰撞过程Eu单离子L-X射线产额与离子入射动能的理论关系.结果表明,射线产额的理论值与实验数据符合得较好.     

电子与原子、离子碰撞过程的相对论效应

在玻恩近似下,建立了高能电子与原子、离于非弹性碰撞过程的相对论性理论计算方法,并以类Li等电子系列为例,阐明了电子与原子、离子非弹性碰撞过程的相对论效应.它包括:1.靶原子的相对论效应,它随原子序数的增加而增大.低z靶(如Li)的相对论效应可以忽略;对Au~(+76)靶的2_3—3p跃迁,广义振子强度相对论性计算值比相应的非相对论性值小27.1%.2.入射电子的相对论效应,它随入射电子能量的增加而增大.对高能入射电子,在特殊角度,要考虑广义振子强度横场项对微分截面的影响.在极端相对论情况下,如入射电子动能 关键词：     

强激光与近临界密度等离子体相互作用中的无碰撞静电冲击波产生

本文通过一维粒子模拟(particle-in-cell)方法研究了强激光与近临界密度等离子体相互作用中的弱冲击波和强冲击波产生,并讨论了非相对论和相对论光强以及等离子体密度分布区间对无碰撞冲击波形成的影响.非相对论的弱驱动光与等离子体相互作用产生的是弱冲击波.由于电子加热不充分,电子能谱呈现出双温分布.较低温度的电子对弱冲击波的形成以及质子反射加速有重要作用.弱冲击波加速质子的能谱呈连续分布.在等离子体密度上升沿区间较大时,可观察到后孤子结构向离子声波结构演化并进一步演化为弱冲击波结构的过程.在相对论的强驱动光强下,电子加热比较充分可达到相对论温度,且呈现出单温分布.进一步分析密度分布区间大小对冲击波形成的影响时发现:1)当等离子体密度上升沿区间较大时,离子声波的势垒易被热电子屏蔽且离子声波结构在传输的过程中容易被后续的激光破坏而无法演化为无碰撞冲击波;2)当等离子密度分布区间较小时,离子声波中加速电场的有效距离(即德拜长度)和持续时间更长,这导致其结构在传输过程中更加稳定.当离子声波中加速的质子与靶后鞘层场加速的质子之间的速度差满足无碰撞冲击波的离子反射条件时,离子声波进一步演化为强...     

Si2+离子与氢原子碰撞电离过程的CTMC计算

应用经典径迹蒙特卡罗方法研究Si2+离子与氢原子碰撞电离反应过程.计算了随入射离子能量变化的总截面、出射电子随角度和能量变化的一阶、二阶微分截面,及出射电子随入射离子能量变化的平均能量.根据计算结果,讨论展示了软碰撞、电子转移到入射离子连续态、两体相遇碰撞等电离机理,阐明了它们对碰撞总截面、微分截面、电离电子能量的影响.通过计算出射电子到入射离子和靶的距离比的电离电子数分布研究了不同入射离子能量"鞍点"电离机理的可能性.     

Collision site effect on the radiation dynamics of cytosine induced by proton

By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions (TDDFT-MD) nonadiabatically in real time, we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 eV to 1000 eV. To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine, two collision sites are specially considered, which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine. Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified. It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations, which are 14.2% and 21.1% of the incident energy respectively. However, the scattering angles show different behaviors in these two situations when the incident kinetic energy increases. When proton collides with O, the scattering angle of proton is larger and the energy lost is more, while proton captures less electrons from O. The calculated fragment mass distribution shows the high counts of the fragment mass of 1, implying the production of H⁺ fragment ion from cytosine even for proton with the incident energy lower than keV. Furthermore, the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.     

Distribution function and electron state density in nonequilibrium plasma created by dye laser

Ultracold nonequilibrium plasma created by a dye laser has been studied by the molecular dynamics method. Electrons and protons in this model of nonequilibrium plasma interacted according to the Coulomb law. In the case of electron-proton interaction and a distance between particles r < a ₀ (Bohr radius), the interaction energy is constant, e ²/a ₀ (e is the charge of electron). An initial proton kinetic energy is set randomly so that the average kinetic energy is 0.01–1 K. Initial full electron energy is also set randomly, but at the same time it is positive; i.e., all the electrons according to our task are located in the continuous spectrum. Average kinetic electron energy per one particle varies from 1 to 50 K. The motion equations in periodical boundary condition for this system have been solved by molecular dynamics method. We have calculated the distribution function in the region near the ionization threshold. The distribution function is being described using electron state density in the nearest neighbor approximation with activity correction.     

Theoretical study on collision dynamics of H+ + H2O at low energies

Scattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.     

The role of d-orbital polarization on rhodium cluster collisions

The effects due to d-orbital polarization in collision processes between a single rhodium atom and a 12 atom rhodium cluster are investigated by means of ab initio molecular dynamics. For the initial configuration of the 12 atom rhodium targets we adopt two different low energy structures. The kinetic energy and impact parameter of the projectile are chosen in such a way that fusion, scattering and fragmentation of the cluster do occur. The collision is treated by means of density functional theory molecular dynamics (DFT-MD). Both spin unpolarized and polarized treatments are implemented in order to clearly distinguish the effects that are due to d-orbital polarization. We find a novel block dynamics, of parts of the cluster, which is due to the directional nature of d-bonds. In addition, the treatment of the collisions by means of high temperature DFT dynamics yields promising minimal energy configurations, which are target dependent but are difficult to obtain otherwise.     

CTMC Investigation of Capture and Ionization Processes in P+H(1s) Collisions in Strong Transverse Magnetic Fields

The collision processes of proton with H(1s) atoms, which is embedded in strong transverse magnetic fields perpendicular to the initial velocity of the projectile, are studied with the classical trajectory Monte Carlo method in the energy range 25 keV /u–2000 keV /u and B ～ 104 T. It is found that the charge exchange cross section is decreased while the ionization cross section is increased significantly. The physics of magnetic field effects is analyzed by the time evolution of electron energy and trajectories, and it is found that these effects are induced by the diamagnetic term in the interaction, continuum electron trapping in the target regions and the Lorentz force. The velocity distributions of the ionized electrons, significantly influenced by the applied fields, are also presented.     

Distribution function and diffusion of electrons in the Rydberg energy space in a nonideal ultracold plasma

The distribution functions and diffusion coefficient of electrons in the Rydberg energy space in an ultracold plasma are obtained as functions of temperature by numerically solving a system of kinetic balance equations. As the initial conditions, the results obtained in previous papers by the molecular dynamics method are used. From calculation of Rydberg electron fluxes, the temperature dependence of the recombination coefficient is obtained, in good agreement with the recombination coefficient calculated previously by the molecular dynamics method.     

Derivation of the density functional theory from the cluster expansion

The density functional theory is derived from a cluster expansion by truncating the higher-order correlations in one and only one term in the kinetic energy. The formulation allows self-consistent calculation of the exchange correlation effect without imposing additional assumptions to generalize the local density approximation. The pair correlation is described as a two-body collision of bound-state electrons, and modifies the electron- electron interaction energy as well as the kinetic energy. The theory admits excited states, and has no self-interaction energy.     

激光作用下薄膜中的电子-声子散射速率

激光功率密度达到太瓦级时，光学激光薄膜破坏中雪崩机制占主导地位. 研究雪崩破坏机理，必然涉及到电子吸收激光能量的速率和电子损耗能量的速率，这些都与电子和声子的散射有密切的联系. 所以，电子受到的散射速率是研究雪崩机制的前提和基础. 本文分析了截断散射声子波矢对散射速率的影响，得到散射速率与电子能量的依赖关系，与其他理论及实验结果一致. 同时还对耦合参数进行了修正，得到了依赖声子波矢的耦合参数，修正结果表明在不改变散射速率与高能电子能量依赖关系的基础上，散射速率整体降低了. 关键词： 激光 薄膜 电子 声子