Excitation and dissociation of tungsten hexacarbonyl W(CO)(6): Statistical and nonstatistical dissociation processes

We have studied the excitation and dissociation processes of the molecule W(CO)(6) in collisions with low kinetic energy (3 keV) protons, monocharged fluorine, and chlorine ions using double charge transfer spectroscopy. By analyzing the kinetic energy loss of the projectile anions, we measured the excitation energy distribution of the produced transient dications W(CO)(6)(2+). By coincidence measurements between the anions and the stable or fragments of W(CO)(6)(2+), we determined the energy distribution for each dissociation channel. Based on the experimental data, the emission of the first CO was tentatively attributed to a nonstatistical direct dissociation process and the emission of the second or more CO ligands was attributed to the statistical dissociation processes. The dissociation energies for the successive breaking of the W-CO bond were estimated using a cascade model. The ratio between charge separation and evaporation (by the loss of CO+ and CO, respectively) channels was estimated to be 6% in the case of Cl+ impact. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3523347]

TIME-DEPENDENT DENSITY FUNCTIONAL STUDY OF MULTIELECTRON TRANSFER IN Cq+-Na-4 COLLISIONS

The process of multielectron transfer from a Na-4 cluster induced by highly charged C6+, C4+, C2+ and C+ ions is studied using the method of time-dependent density functional theory within the local density approximation combined with the use of pseudopotential. The evolution of dipole moment changes and emitted electrons in Na-4 isobtained and the time-dependent probabilities with various charges are deduced. It is shown that the Na-4 cluster is strongly ionized by C6+ and that the number of emitted electrons per atom of Na-4 is larger than that of Na-2 under the same condition. One can find that the detailed information of the emitted electrons from Na-4 is different from the same from Na-2, which is possibly related to the difference in structure between the two clusters.

电子入射氦原子的双电离的实验研究

反应显微成像谱仪能够在全空间范围内探测碰撞反应后全部荷电出射粒子的动量信息，本论文基于适用于低能电子入射原子的双电离或多重电离的反应显微成像谱仪，对电子入射氦原子的双电离反应机制进行了实验研究。论文着重对适用于低能电子入射原子的双电离的反应显微成像谱仪及其特性进行介绍，并介绍和讨论了目前几种计算原子的双电离微分截面的理论模型。通过对106eV电子入射氦原子的双电离实验结果进行分析讨论，获得了以下结果：1，反应后出射电子的空间分布特征及电子间夹角的分布特征，显示出Wannier提出的原子的双电离反应机制的部分特性，从而验证了Wannier对近阈值下原子的双电离机制的推断。2，实验获得的五重微分截面与不同理论模型的计算结果进行了比较，研究表明DS6C理论模型能够对近阈值下氦原子的双电离进行较好的描述

中低能区He2++He碰撞反应转移电离机制研究

反应显微成像谱仪能够对离子-原子碰撞反应中的末态产物进行运动学完 全测量。本论文基于反应显微成像谱仪对70-400keV He 2+ -He 碰撞中转移电离机 制进行了实验研究。 通过对不同出射角度电子的能谱研究表明， ECC电子和速度分布在0和入射 炮弹速度之间的“分子化”特征电子是出射电子能谱的主要贡献，前者是动力学 两步过程的作用，后者可由“准分子”激发模型给予定性解释，“鞍点电子”仅 是后者的一部分。通过对不同平面内出射电子的速度分布研究发现出射电子主要 集中在散射平面内，而且其速度分布介于0与炮弹速度之间且前向出射，同时在 炮弹与靶核核间轴处有一极小值；在入射离子能量较低时，出射电子空间分布较 为对称，随着入射离子能量的增加，出射电子逐渐靠近炮弹或靶核；与此同时， 由于 态电子与 态电子相互干涉，出射电子在散射平面内的分布还与碰撞参数 相关，在大碰撞参数下， 态电子的作用更加明显，而在小碰撞参数下 态电子 的作用更加显著。实验结果表明准分子激发和动力学两步过程是中低能He2+ -He 转移电离过程的两种主要机制。

96 MEV能量下~(16)O + ~(94)Ni反应机制研究

The pro sectile-like fragments of ~(16)O + ~(64)Ni Reaction (Elab = 96 MeV) were measured by using ionization chamber telescopes. The countour plots of d~36/dndEdz in TKE-θ plane angular distribution integrating over different TKE window. The z-distribution and angular distributions of different fragments from He to O were obtained. The main mechanisms dominating in this reaction were discussed

Dynamics of excited m-dichlorobenzene

Dynamics of excited m-dichlorobenzene is investigated in real time by femtosecond pump-probe method, combined with time-of-flight mass spectrometric detection in a supersonic molecular beam. The yields of the parent ion and daughter ion C6H4CI+ are examined as a function of the delay between the 270 and 810 nm femtosecond laser pulses, respectively. The lifetime of the first singlet excited state S-1 of m-dichlorobenzene is measured. The origin of this daughter ion C6H4CI+ is discussed. The ladder mechanism is proposed to form the fragment ion. In addition, our experimental results exhibit a rapid damped sinusoidal oscillation over intermediate time delays, which is due to quantum beat effects.