Dissociation of alkane ionized molecules

The subject of investigation is the fragmentation of variously charged molecular ions arising in col-lisions of several kiloelectronvolt H⁺, He²⁺, and Ar⁶⁺ ions with molecules of the simplest alkanes (from methane to butane). Using the method of time-of-flight mass spectrometry, the formation cross sections of dissociation-induced fragment ions are measured. The dissociation takes place when an incident ion captures an electron from a methane, ethane, or propane molecule. The role of additional ionization of the molecule, which accompanies the electron capture by the incident ion, is elucidated. The kinetic energy spectrum for protons resulting from the fragmentation of multiply charged alkane ions is determined. The most plausible kinetic energies of protons depending on the degree of ionization and molecule size fall into the range 1–25 eV. It is shown that, when the molecule loses several electrons, the kinetic energies of protons are governed by Coulomb interaction between all fragment ions and are determined by their flying apart from the relative spatial arrangement of corresponding atoms in a parent molecule.     

Interaction of <Superscript>3</Superscript>He<Superscript>2+</Superscript> and Ar<Superscript>6+</Superscript> ions with acetylene,ethylene, and ethane molecules

Time-of-flight mass spectroscopy methods are employed for studying processes occurring during capture of electrons by ³He²⁺ and Ar⁶⁺ multiply charged ions with energy 6z keV (z is the ion charge) from C₂H _n molecules (n = 2, 4, 6) with different multiplicities of C-C bonds. Fragmentation schemes of the molecular ions formed in such processes are established from analysis of correlations of recording times for all fragment ions. The absolute values of the cross sections of capture of an electron and capture with ionization are measured, as well as the cross sections of formation of fragment ions in these processes. The absolute values of total capture cross sections for several electrons are determined.     

Creating Ti:Al<Subscript>2</Subscript>O<Subscript>3</Subscript> media with pinched beams of electrons and Ti<Superscript><Emphasis Type="Italic">n</Emphasis>+</Superscript> ions

The collective acceleration of multiply charged titanium ions on pinched electron beams and the mechanisms of titanium ion implantation into sapphire crystals are studied. Efficient Ti³⁺ ion implantation is achieved by irradiating sapphire crystals with high current picosecond beams of electrons and Ti ⁿ⁺. The ions are shock-implanted into regular positions of the crystalline lattice, replacing Al³⁺ ions.     

纳秒激光电离分子团簇产生高离化离子的激光波长效应

 利用脉冲分子束-激光电离-飞行时间质谱仪,在10⁹～10¹² W·cm^-2激光功率密度条件下,考察了Nd：YAG激光器输出的1 064,532,266 nm波长的激光与苯、氨、硫化氢等团簇的相互作用。发现1 064 nm的激光可以电离分子束产生高离化态的C⁴⁺,N⁵⁺,S⁶⁺等离子;波长为532 nm的激光则电离产生价态较低的C³⁺,C²⁺,N³⁺,N²⁺, S⁴⁺,S³⁺以及S²⁺ 等离子;在266 nm波长条件下进行实验,没有产生任何高价离子。提出了一个“多光子电离引发-逆轫致吸收加热-电子碰撞电离”模型来解释高价离子的产生。激光场下电子在团簇内部的逆轫致加热是整个过程的关键步骤,电子被加热的速度正比于激光波长的平方。这可以解释为何长波长的激光有利于更高价态离子的产生。     

纳秒强激光中丙酮团簇增强的多价电离现象

利用脉宽为25 ns的脉冲Nd: YAG 532 nm的激光，在10¹⁰—10¹¹ W/cm²的强度下，用飞行时间质谱对丙酮团簇的激光电离过程进行了研究. 观察到了较强的O^q+(q=2—4)和C^q+(q=1—4)高价离子信号，这些高价离子 C⁴⁺，C³⁺，C²⁺，O⁴⁺，O³⁺，O²⁺的最大概然平动能分别为240 eV，70 eV，30 eV，90 eV，80 eV，40 eV. 高价离子的强度和平动能随激光强度的增大而增大. 我们提出一个多光子电离引发，逆韧致吸收加热-电子碰撞电离模型来解释高价离子的产生. 关键词： 丙酮 团簇 库仑爆炸 高价离子     

电离效率对激光电离团簇的高价离子产物的影响

纳秒激光与团簇相互作用产生高价离子逐渐成为分子物理界的热点之一, 为了深入研究团簇电离的本质, 本文以分子结构相似、元素组成相同的苯、环己烯和环己烷的分子团簇为对象, 利用飞行时间质谱研究了其与5 ns的532 nm激光相互作用时电离产物的价态和强度分布. 结果表明: 这三种化合物多光子电离效率苯>环己烯>环己烷, 但其高价离子的价态和比值苯是最低的, 环己烷的碳离子最高价态为4价, C³⁺和C²⁺的比值为1.1; 环己烯电离产物C³⁺和C²⁺ 的比值降低为0.6; 苯团簇的最高价态只有3价, C³⁺和C²⁺的比值约为0.4. 引起这种现象的原因可以归结于高的多光子电离效率会导致团簇多位点的电离, 引起团簇在电子加热到发生碰撞电离之前发生解离, 减小了团簇的尺寸, 进而减少了离子发生碰撞电离产生高价离子的反应时间, 最终阻碍了高价态离子的产生.     

乙醚团簇在纳秒激光场中的多价电离及其电子能量分布的研究

用5ns,1064nm的脉冲Nd:YAG激光,研究了乙醚团簇与纳秒激光的相互作用.在10¹¹ W/cm²量级光强下,观察到价电子完全剥离的O⁶⁺,C⁴⁺,且这些高价离子的强度比值基本不随激光能量而变化.用阻滞电压方法测量了电离过程中溢出电子能量分布,在最大激光能量4.0×10¹¹ W/cm²,溢出电子的平均能量为56eV,最大能量为102eV.实验结果支持了高价离子产生的“多 关键词： 高价离子 电子能量 纳秒激光 乙醚团簇     

Non-adiabatic interactions in charge transfer collisions

An analysis of the charge transfer mechanism in the collision of multiply charged ions with molecular and biomolecular targets is performed, considering the non-adiabatic interactions between the molecular states involved. Collisions of doubly charged C ²⁺ ions on small molecular targets, CO and OH, have been investigated, together with the analysis of charge transfer between C ⁴⁺ ions on uracil and halouracil biomolecular targets. The process is studied theoretically by means of ab-initio molecular calculations followed by a semi-classical treatment of the collision dynamics. The influence of rotational couplings is discussed with regard to the collision energy. Strong anisotropic and vibration effects are pointed out.     

Ellipticity-dependent of multiple ionisation methyl iodide cluster using 532 nm nanosecond laser

The dependence of multiply charged ions on laser ellipticity in methyl iodide clusters with 532 nm nanosecond laser was measured using a time-of-flight mass spectrometer. The intensities of multiply charged ions I^q+(q = 2–4) with circularly polarised laser pulse were clearly higher than those with linearly polarised laser pulse but the intensity of single charged ions I⁺ was inverse. And the dependences of ions on the optical polarisation state were investigated and a flower petal and square distribution for single charged ions (I⁺, C⁺) and multiply charged ions (I²⁺, I³⁺, I⁴⁺, C²⁺) were observed, respectively. A theoretical calculation was also proposed to simulate the distributions of ions and theoretical results fitted well with the experimental ones. It indicated that the high multiphoton ionisation probability in the initial stage would result in the disintegration of big clusters into small ones and suppress the production of multiply charged ions.     

Many-body effects in the formation of multiply charged ions in a strong laser field

Some of the many-body effects in the formation of multiply charged ions in a laser field have been taken into account: inelastic tunneling, collective tunneling, and magnetic moment projection relaxation of the atomic core. Strong fields with an intensity exceeding 10¹⁷ W cm⁻² are considered when the magnetic component of the laser field acts on the free motion of a photoelectron; therefore, the formation of multiply charged ions through rescattering becomes unlikely. Numerical calculations have been performed for Ar⁹⁺ … Ar¹³⁺, Kr¹⁹⁺ … Kr²³⁺, Rb¹⁰⁺, and Rb¹¹⁺ ions. A significant contribution of collective tunneling, which was not observed in weaker fields investigated previously, has been revealed. Allowance for collective tunneling is shown to reduce the intensity leading to saturation by more than 10%. In this case, the yield of multiply charged Rb ions changes by an order of magnitude, while the yield of multiply charged Ar and Kr ions changes by more than a factor of 2. Comparison with experimental data on the formation of argon ions under the action of a linearly polarized laser pulse is made.     

Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

Recombination processes in atomic clusters irradiated by superintense femtosecond laser pulses

Various mechanisms of recombination of electrons with multiply charged atomic ions in atomic clusters irradiated by superintense femtosecond laser pulses are discussed. All of the recombination mechanisms are shown to take a time considerably longer than the laser pulse duration and, hence, they can develop only in a homogeneous, fairly rarefied cluster plasma after pulse termination. All autoionization states of multiply charged ions in a dense cluster plasma have been found to be destroyed by the Holtsmark electric field.     

The SMILETRAP (Stockholm-Mainz-Ion-LEvitation-TRAP) facility

Described in this paper is an experimental facility which measures atomic masses by using multiply charged ions from an electron beam ion source. The ions are injected into a Penning trap and the cyclotron frequencies measured. A precision of 2×10^–9 has been reached using highly charged carbon, nitrogen, oxygen and neon.     

Two-photon excitation/ionization of deep shells of multiply charged atomic ions

Absolute values and the shape of cross sections for two-photon one-electron excitation/ionization of the 1s shell of Ne⁶⁺ and Ne⁸⁺ ions, taking into account the relaxation of the atomic core in the field of resulting vacancies, are calculated. The many-particle stabilization of a deep vacancy in moving from a neutral atom to multiply charged ions is taken into account. The calculations are made for linear and circular polarizations of the incident laser beam. The results of the calculations are predictive.     

Double ionization of atoms by multiply charged ions and a strong electromagnetic field: Effects of correlation in the continuum

A nonstationary theory of double ionization of two-electron atoms in collisions with multiply charged ions or by an intense electromagnetic field is developed. An approach that permits investigating both problems by a single method is formulated. A two-electron continuum wave function that takes into account the interaction of the electrons with the atomic nucleus and the external ionizer as well as with one another is obtained as a product of Coulomb waves with modified Sommerfeld parameters. The computational results obtained for the double ionization of helium atoms by multiply charged ions are in good quantitative agreement with the existing experimental data. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 23–26 (10 July 1997)     

类钴氙离子入射Ni表面激发的红外光谱线和X射线谱

当高电荷态类钴氙离子（cobalt like -Xe, Xe²⁷⁺）入射金属Ni表面过程中,共振电子俘获释放势能完成中性化,形成多激发态的Xe原子,其外壳层电子退激辐射红外光谱线.入射离子特殊的势能释放方式、离子动能和金属表面引起离子增益的能量在极短的时间（飞秒量级）沉积靶平方纳米尺度的空间范围,引起靶表面原子激发和电离,形成复杂组态之间的跃迁,特别是偶极禁戒跃迁（电四极跃迁、磁偶极跃）和X射线发射.单离子X射线产额随入射离子的动能增加而增加. 关键词： 高电荷态离子 红外光谱线 X射线 禁戒跃迁     

Kinetic energy distributions of the fragment ions from multiply ionized C2H6 as functions of the charge state of the intermediate states

Here, we report the kinetic energy distributions (KEDs) of the fragment ions produced from multiply ionized ethane (C₂H₆) molecules in single electron capture collisions with 1.2 MeV C²⁺. To systematically investigate the fragmentation dynamics, the KEDs were obtained as functions of the charge state of the intermediate C₂H₆^r+* ions r transiently generated prior to fragmentation. r was determined from coincidence measurement of the fragment ions and the number of emitted electrons. The KEDs are drastically different depending on the number of broken C–H bonds. The underlying causes are explained by the variation of the relative contributions of the multiply ionized states and preferential fragmentation pathways. For instance, CH_n⁺ fragment ions with smaller n exhibit lower KEs because they are likely to be correlated with H⁺ emission, which carries away a large portion of the KE release. In addition, we report the KEDs of H₃⁺ produced from doubly and triply charged states.     

中等光强纳秒激光电离苯团簇产生多价碳离子的数值模拟和实验研究

飞秒强激光与团簇相互作用产生多价离子的现象已被广泛报道,然而近期多个研究小组发现当功率密度低至1010W/cm2的纳秒激光照射团簇时,同样也观察到了多价离子的存在.虽然可以用"多光子电离引发-逆韧致吸收加热-电子碰撞电离"电离机理对这种现象进行解释,但是缺乏相应的数值模拟.建立了一个简化的数值模型,根据有质动力势Up计算团簇内电子能量,再由Lotz公式计算出相应的电离截面,最后由动力学反应速率方程计算出团簇内多价碳离子随时间的演变.详细分析了团簇尺寸、电子密度等关键参数对多价离子产生的影响.数值模拟结果表明:团簇电离在小于0.7 ns时间尺度内完成,C2+,C3+和C4+多价离子强度达到平衡后,离子相对强度由大到小依次为C2+,C3+,C4+,这与实验结果相一致;多价离子的价态随着团簇尺寸的增加而升高,半径为5.6 nm的苯团簇比半径为3 nm的苯团簇更容易产生高价态的离子,这也与实验结果相一致.     

Multi-reference configuration-interaction calculations on multiply charged ions of carbon monosulfide

The potential energy curves for neutrals and multiply charged ions of carbon monosulfide are computed with highly correlated multi-reference configuration interaction wavefunctions.The correlations of inner-shell electrons with the scalar relativistic effects are included in the present computations.The spectroscopic constants,dissociation energies,ionization energies for ground and low-lying excited states together with corresponding electronic configurations of ions are obtained,and a good agreement between the present work and existing experiments is found.No theoretical evidence is found for the adiabatically stable CSq+(q>2) ions according to the present ab initio calculations.The calculated values for 1st-6th ionization energies are 11.25,32.66,64.82,106.25,159.75,and 224.64 eV,respectively.The kinetic energy release data of fragments are provided by the present work for further experimental comparisons.     

CS2团簇增强的激光多价电离现象的质谱研究

利用脉宽为25ns的脉冲Nd: YAG 532 nm的激光，在8×10¹⁰W/cm²的强度下，用飞行时间质谱对CS₂的激光电离过程进行了研究.观察到了较强的C²⁺和S²⁺高价离子信号，这些高价离子C²⁺，S²⁺的最可几平动能高达144 eV，112 eV.不同进样方式，激光延迟以及束源压力的实验结果表明，这些高价离子可能来源于CS₂团簇的库仑爆炸过程.多光子电离引发，逆韧致吸收加热-电子碰撞电离模型可能是高价离子产生的机理. 关键词： 2')" href="#">CS₂ 团簇 高价离子 激光电离