尾流效应对快速双原子分子离子在固体中电荷态及分子轴取向的影响

研究了快速双原子分子离子在固体中穿行时,尾流效应对各离子电荷态以及库仑爆炸过程的影响.借助于线性介电响应理论和局域介电函数,离子之间的动力学相互作用势可以表示成对称的屏蔽库仑势和非对称的尾势.通过对分子离子上所有束缚电子的总能量进行变分和求解单个离子的运动方程,自洽地确定出分子离子中每个离子的电荷态.数值结果表明,由于尾流效应的影响,在初始穿行阶段,分子离子中导航离子的电荷数随穿行深度的增加而单调递增,而尾随离子的电荷数则随穿行深度的增加而振荡.但当穿行深度很大时,两个离子的电荷数都趋于具有相同速度的孤立离子的电荷数.此外,还发现分子轴的取向朝入射速度方向偏转.     

利用快分子离子与固体的相互作用对H2+,HD+和D+2结构的研究

利用快分子离子与固体的相互作用,依靠一套高分辨装置,测量了H2+,HD+和D2+的结构,得到其核间距分别为1.19±0.003 nm、1.25±0.003 nm和1.32±0.003 nm.通过对比,证实了分子离子结构中同位素效应的存在,分析了实验值和理论值存在差别的原因,讨论了实验结果中同位素效应产生的缘由.     

激光场对快速分子离子与固体相互作用的影响

利用线性化的流体力学方程和泊松方程，描述了在强激光场作用下快速分子离子在固体中产生的电激发过程，并推导出分子离子中两个离子之间的动力学相互作用势和相互作用力的一般表达式.通过数值求解离子的运动方程，研究了激光场的参量对分子离子库仑爆炸过程和能量损失的影响. 关键词： 激光场 分子离子 库仑爆炸 能量损失     

利用尾流效应确定HD2+的结构与核间距

在研究HD2+ 与固体膜的相互作用时, 发现在HD2+ 穿过固体时产生了较强的尾流效应, 并在确定HD2+作的结构时, 尾流效应起到了关键的作用. 这一技术的使用, 可以使得许多使用传统方法无法确定的分子离子结构寻求到一种方法和手段. 本文就如何使用尾流效应来确定HD2+ 结构作一报道. 这种方法的基本思想是,库仑爆炸能谱图普相对于分子离子的核间距时非常是非常敏感的.     

利用尾流效应确定HD2+的结构与核间距

在研究HD2+ 与固体膜的相互作用时, 发现在HD2+ 穿过固体时产生了较强的尾流效应, 并在确定HD2+作的结构时, 尾流效应起到了关键的作用. 这一技术的使用, 可以使得许多使用传统方法无法确定的分子离子结构寻求到一种方法和手段. 本文就如何使用尾流效应来确定HD2+ 结构作一报道. 这种方法的基本思想是,库仑爆炸能谱图普相对于分子离子的核间距时非常是非常敏感的.     

高电荷态离子引发氮气分子的解离和碎裂

利用时间和位置灵敏相关的符合装置,实验研究了高电荷态Xeq (q=15-21)离子与N2分子慢碰撞过程的多电子转移过程、N2 离子的解离以及N2q (1相似文献   

异构微团簇库仑爆炸中较重离子尾流效应’消失’的研究

快微团簇穿过固体时和固体发生相互作用过程中,尾流效应是一个显著的特性。但由不同元素或原子构成的异构微团簇和固体作用分解后,其较重离子的能谱往往很难观察到尾流现象,这是一个倍感困惑的实验现象。本文系统研究了异构微团簇库仑爆炸中较重离子尾流效应表现不明显甚至’消失’的缘由。通过理论推算结合实验过程以及与实验条件等的综合研究,论证出分辨因素、计数差因数和作用力因素是造成这种反常现象的主要原因,给出了完整的分析。并以HD+、HD2+等离子为例,对库仑爆炸实验中异构微团簇在以上三个因素方面的产物采样、发散等过程做了较详细论述和说明。将对以后从事该领域的研究工作具有借鉴和参考意义。     

HD2+通过超薄碳膜的"尾流"效应

快分子离子穿过固体时会产生库仑爆炸(Coulomb Explosion),尾流效应是库仑爆炸中的一个显著特性.HD2 的爆炸能谱在实测中发现了一些引人注目的特性:1)H 的尾流效应特别显著;2)H 的能谱结构非常类似HeH 中H 的能谱;3)尾流效应在D 的能谱中体现得很弱.这些特性对分析了解HD2 的结构和物理化学性质有很大的帮助.本文依照“尾流”效应(Wake Effect)的等离子体模型,将爆炸中两个D 产物的尾流场近似认为一个He 的尾流场,模拟计算了1.4977 MeV HD2在100 nm碳膜中分解后0°方向的能谱形式.给出了相同条件下的实验结果,得到了非常接近的结果,并将两者作了比较和分析.文中同时给出了D 的实验能谱,对D 的尾流效应相对较弱作了分析,指出对不同产物分辨的差异、产物的非直线运动等是造成D 尾流效应弱的原因.     

高电荷态离子入射Al表面库仑势对靶原子特征谱线强度的影响

用同一动能(150keV)而不同电荷态的⁴⁰Ar^q+(8≤q≤16)离子入射金属Al表面，靶原子受激辐射产生特征光谱线. 实验结果表明：高电荷态离子与金属表面相互作用过程中，经过与靶原子碰撞(Penning碰撞)交换动能和共振电子俘获(resonant capture)释放库仑势能，将携带的能量沉积于靶表面，使靶原子激发. 这种激发不同于光激发，它不仅激发了原子复杂电子组态之间的跃迁，而且跃迁辐射的特征谱线强度增强的趋势与入射粒子的库     

高电荷态离子入射Al表面库仑势对靶原子特征谱线强度的影响

用同一动能(150keV)而不同电荷态的⁴⁰Ar^q+(8≤q≤16)离子入射金属Al表面,靶原子受激辐射产生特征光谱线. 实验结果表明：高电荷态离子与金属表面相互作用过程中,经过与靶原子碰撞(Penning碰撞)交换动能和共振电子俘获(resonant capture)释放库仑势能,将携带的能量沉积于靶表面,使靶原子激发. 这种激发不同于光激发,它不仅激发了原子复杂电子组态之间的跃迁,而且跃迁辐射的特征谱线强度增强的趋势与入射粒子的库 关键词： 高电荷态离子 库仑势 特征光谱 光谱强度     

Multiple charge states of titanium ions in laser produced plasma

An intense laser radiation (10¹² to 10¹¹ W/cm⁻²) focused on the solid target creates a hot (≥1 keV) and dense plasma having high ionization state. The multiple charged ions with high current densities produced during laser matter interaction have potential application in accelerators as an ion source. This paper presents generation and detection of highly stripped titanium ions (Ti) in laser produced plasma. An Nd:glass laser (KAMETRON) delivering 50 J energy (λ=0.53 μm) in 2.5 ns was focused onto a titanium target to produce plasma. This plasma was allowed to drift across a space of ∼3 m through a diagnostic hole in the focusing mirror before ions are finally detected with the help of electrostatic ion analyzer. Maximum current density was detected for the charge states of +16 and +17 of Ti ions for laser intensity of ∼10¹¹ W/cm⁻².     

Effect of gold electrode crystallographic orientations on charge transport through aromatic molecular junctions

ABSTRACT

We examined the electrical conduction through single-molecular junctions comprising of anthracenedithiol molecule coupled to two gold electrodes having ?1,0,1?, ?1,1,0? and ?1,1,1? crystallographic orientations. Owing to this jellium model, we evaluated the values of current and conductance using non-equilibrium Green's functions combined with extended Huckel theory. This data was further interpreted in terms of transmission spectra, density of states and their molecular orbital analysis for zero bias. We evinced the oscillating conductance in all three cases, due to the oscillation of orbital energy relative to Fermi level. Our detailed analysis suggested that electrode orientation can tune the molecule–electrode coupling and hence conduction. Anthracene molecular junction with ?1,1,0? orientation displayed favourable conduction, when compared to the other two orientations, thus can provide us an insight while designing futuristic molecular electronic devices.     

Studies on the full vibrational energy spectra for some electronic states of diatomic molecular ions XY+

The first accurate studies on the vibrational spectroscopic constants and the corresponding full vibrational energy spectra of some electronic states of diatomic molecular ions XY⁺ were performed using algebraic method(AM). The AM is applied on the X¹Σ⁺ state of BeH⁺, the X²Σ⁺ state of CO⁺, the X²Π_g state of F ₂ ⁺ , the A²Π_u state of O ₂ ⁺ and the X²Σ _g ⁺ state of Li ₂ ⁺ . The results show that AM can generate accurate vibrational spectroscopic constants as well as accurate full vibrational energy spectra by using some accurate experimental vibrational energies, and that the AM vibrational energies are better than other theoretical data. __________ Translated from Chinese Journal of Atomic and Molecular Physics, 2005, 22 (4) (in Chinese)     

双原子分子离子XY+部分电子态完全振动能谱的精确研究

关于双原子分子离子XY 的完全振动能谱,目前还没有实验和理论的数据报道。本文首次应用代数方法AM(Algebraic Method),获得了BeH -X1Σ 态,CO -X2Σ 态,F2 -X2Πg态,O2 -A2Πu态和Li2 -X2Σg 态的精确振动光谱常数和完全振动能谱,解决了实验方法和精确量子力学理论方法难以获得双原子分子离子XY 的包含最高振动能级在内的所有高阶振动能级的精确数值这一问题。所有研究结果表明:由部分较低的实验精确振动能级,可用AM产生双原子分子离子XY 的精确振动光谱常数和包含全部激发态的完全振动能谱;所得的AM振动能谱比其他理论方法得到的结果更好。     

Semi-empirical calculations for the ranges of fast ions in silicon

A semi-empirical method is proposed to calculate the ion ranges in energy region E?=?0.025–10?MeV/nucleon. The dependence of ion ranges on the projectile nuclear charge, mass and velocity is analysed. The calculations presented for ranges of ions with nuclear charges Z?=?2–10 in silicon are compared with SRIM results and experimental data.     

Magnetic field effects on excited states,charge transport,and electrical polarization in organic semiconductors in spin and orbital regimes

Magnetic field can influence photoluminescence, electroluminescence, photocurrent, injection current, and dielectric constant in organic materials, organic–inorganic hybrids, and nanoparticles at room temperature by re-distributing spin populations, generating emerging phenomena including magneto-photoluminescence, magneto-electroluminescence, magneto-photocurrent, magneto-electrical current, and magneto-dielectrics. These so-called intrinsic magnetic field effects (MFEs) can be observed in linear and non-linear regimes under one-photon and two-photon excitations in both low- and high-orbital materials. On the other hand, spin injection can be realized to influence spin-dependent excited states and electrical conduction via organic/ferromagnetic hybrid interface, leading to extrinsic MFEs. In last decades, MFEs have been serving as a unique experimental tool to reveal spin-dependent processes in excited states, electrical transport, and polarization in light-emitting diodes, solar cells, memories, field-effect transistors, and lasing devices. Very recently, they provide critical understanding on the operating mechanisms in advanced organic optoelectronic materials such as thermally activated delayed fluorescence light-emitting materials, non-fullerene photovoltaic bulk-heterojunctions, and organic–inorganic hybrid perovskites. While MFEs were initially realized by operating spin states in organic semiconducting materials with delocalized π electrons under negligible orbital momentum, recent studies indicate that MFEs can also be achieved under strong orbital momentum and Rashba effect in light emission, photovoltaics, and dielectric polarization. The transition of MFEs from the spin regime to the orbital regime creates new opportunities to versatilely control light-emitting, photovoltaic, lasing, and dielectric properties by using long-range Coulomb and short-range spin–spin interactions between orbitals. This article reviews recent progress on MFEs with the focus on elucidating fundamental mechanisms to control optical, electrical, optoelectronic, and polarization behaviors via spin-dependent excited states, electrical transport, and dielectric polarization. In this article both representative experimental results and mainstream theoretical models are presented to understand MFEs in the spin and orbital regimes for organic materials, nanoparticles, and organic–inorganic hybrids under linear and non-linear excitation regimes with emphasis on underlying spin-dependent processes.     

Rotational effects in low energy dissociative recombination of diatomic ions

The effect of rotational interaction in the low energy dissociative recombination process of diatomic molecules has been explored for typical molecular ions () which sample a large range of molecular masses. We show that rotation plays a role mainly for the indirect recombination process through bound Rydberg states, and for light molecules. When the direct process based on a strong electronic interaction is fast and dominating, rotational couplings can be safely neglected especially for heavier molecules like NO. Received: 18 September 1997 / Revised in final form: 17 October 1997 / Accepted: 20 October 1997     

Comparative study of various stopping power formulations for heavy ions in solids

A comparative study of different energy loss formulations viz. Benton and Henke, Mukherjee and Nayak, Zieglar et al. and Hubert et al. has been done at lower energies (0.5 to 5 MeV/n) with the aim to identify their relative validity in this energy range. Calculated results using these formulations have been compared with experimental results available in literature.