超短强激光脉冲与H2＋相互作用研究：经典与量子计算的比较

用经典动力学和量子力学方法分别研究了Ｈ２＋在超短强激光场中的电离、离解和残存行为，得到了相似的结果：即在超短强激光脉冲作用下，Ｈ２＋的电离占优，但有限的量子计算低估了Ｈ２＋的离解几率；而经典处理则没有显示Ｈ２＋在超强场中的稳定化。另外，经典计算表明当核间距Ｒ伸展到一定范围时，Ｈ２＋的电离率最大。这符合量子计算中发现的电荷谐振增强电离（ＣＲＥＩ）现象。     

丙酮分子的分质量共振多光子电离光谱及多光子电离—离解机理研究

用多光子电离飞行时间质谱法三光子与丙酮分子３ｄ形态和４ｓ态共振的激光波长区域获得了丙酮分子的共振多光子电离分质量多光子电离（ＭＰＩ）光谱和飞行时间质谱，实验观察到的主要产物是ＣＨ３ＣＯ＾＋和ＣＨ＾＋３，还观察到了少量的Ｃ＾＋，ＣＨ＾＋，ＣＨ＾＋２和ＣＨＯ＾＋，在实验的激光波长范围内未见到母体离子，分质量多光子电离光谱具有相似的光谱结构，几个主要谐峰分别对应着（ｎ０，３ｄ）和（ｎ０，４ｓ）里德堡跃迁     

紫激光作用下四甲基硅多光子电离TOF质谱研究

本文采用超声分子束技术，以飞行时间质谱仪，在３９６～３８７ｎｍ内的紫激光作用下对四甲硅进行了多光子电离飞行时间质谱的研究，在较高在激光能量作用下检测到了Ｓｉ（ＣＨ３）＾＋ｎ（ｎ＝１，２，３，）、Ｓｉ＾＋及Ｃ＾＋２等多种离子的信号，在较低的激光能量作用下只检测到了Ｓｉ＾＋、Ｃ＾＋２等离子的信号，表明四甲基硅在不同激光能量作用下经历了不同的多光子电离过程。     

N2分子X^1Σg^＋,A^3Σu^＋和B^3Пg的势能函数

用文献［１，２，８］介绍的方法推导了Ｎ２分子的基态（Ｘ＾１Σｇ＾＋）的激发态（Ａ＾３Σｕ＾＋和Ｂ＾３Пｇ）的合理离解极限。计算并比较了在６－３１１Ｇ＾＊基集合，ＵＨＦ、ＣＩＤ、ＵＣＩＳＤ和ＱＣＩＳＤ水平下Ｎ２分子上述三个电子态的平衡结构和谐振频率；并用ＱＣＩＳＤ／６－３１１Ｇ＾＊计算了各态的系列单点势能值，由正规方程组拟合Ｍｕｒｒｅｌｌ－Ｓｏｒｂｉｅ函数得到了相应各态的完整势能函数，结果与实验数计     

HD^＋核间距及基态势能曲线的排列通道量子力学计算

依据排列通道量子力学（ＡＣＱＭ）的基本原理，对分子离子ＨＤ＾＋的核间距和基态势能曲线以及离解能Ｄｅ做了量论计算，得到了ＨＤ＾＋的核间距为２．０７２５ａｏ，并求得ＨＤ＾＋按两种方式离解时的势能曲线，认为多数ＨＤ＾＋应按Ｈ＾＋＋Ｄ的方式离解。通过比较计算，文章认为ＨＤ＾＋比Ｈ２＾＋更容易激发和离解，也更不稳定。同时文章对用ＡＣＱＭ解决非对称的同位素微团簇的一般方法做了简明阐述。     

激光诱发SiH4＋CH4等离子体的发射光谱

本工作采用光学发射谱方法测量了ＴＥＡ ＣＯ２脉冲激光辐射ＳｉＨ４＋ＣＨ４系统产生的等离子体反应过程中的发射谱特性，探测到了Ｓｉ，Ｓｉ＾＋，Ｓｉ＾２＋，Ｃ，Ｃ＾＋，Ｃ＾２＋，ＣＨ，ＳｉＨ，ＳｉＨ＾＋，Ｓｉ２和Ｈ的特征辐射，研究了含Ｃ，Ｓｉ碎片粒子光谱随实验条件的变化规律，并讨论了反应条件对ＯＥＳ的影响。     

飞行时间质谱仪中激光解离的Ni^＋与醇类化合物分子束流气 …

将分子束流,激光解离和飞行时间质谱结合起来,在一个石英反应室内,让激光解离的Ｎｉ＾２＋与连续喷入的醇分子不流发生反应,产物经飞行时间质谱仪检测,研究了Ｎｉ＾＋一Ｃ２～Ｃ６等五种醇分子的气相反应。用如下的插入机理解释反应：（１）选择性的插入醇分子共价键;（２）β－Ｈ迁移至Ｎｉ＾＋;（３）失去一中性分子形成产物离子。     

自由基和激发态原子分子反应装置

自由基和激发态原子分子反应装置是一台综合了分子束技术，激光诱导荧光技术，共振多光子电离技术及质谱和化学发光光谱测量技术相结合的功能比较齐全的分子反应动力学研究装置。利用稀有气体（Ｈｅ，Ａｒ，Ｘｅ）亚稳态与Ｎ２，ＣＳ２等分子碰撞传能发射光谱测量及Ｃ（＾３Ｐ）＋Ｎ２Ｏ（Ｘ＾１Σ＾＋）反应产物ＣＮ（Ｘ＾２Σ＾＋，Ｖ＾ｎ）的激光激发谱测定证实了这台装置具有良好的工作性能。并将装置分为超音束源，质谱室及激光     

NaF及其掺杂晶体F2心的二向色性研究

给出了ＮａＦ及其掺杂质Ｌｉ＾＋、Ｍｇ＾２＋、Ｃｕ＾２＋和ＯＨ＾－五种样品的Ｆ２心在偏振的氮分子激光照射下的二向色性吸收特性，对各种样品中Ｆ２心的转向效率进行了比较，并对结果进行了机理性的分析。     

AlH2（X^2A1）体系的结构与势能函数

在ＱＣＩＳＤ／６－３３１＋＋（３ｄｆ,３ｐｄ）水平上,优化出ＡｌＨ２（Ｘ＾２Ａ１）分子稳定构型为Ｃ２ｖ,其平衡核间距Ｒｅ＝１．５９２Ａ、∠ＨＡｌＨ－１１８．６８°,同时也计算出振动频率。在此基础上,根据微观可逆性原则,正确地判断了离解极限。使用多体项展式理论方法,导出了基态ＡｌＨ２（Ｃ２ｖ）平衡结构,然后根据势能函数等值图讨论了Ｈ＋ＡｌＨ反应和Ａｌ＋Ｈ２反应的势能面静态特征。结果表明在Ｈ＋ＡｌＨ及     

Dissociation and ionization of H+2 by ultrashort intense laser pulses probed by coincidence 3D momentum imaging

Laser-induced dissociation and ionization of H(+)(2) were simultaneously measured using coincidence 3D momentum imaging, allowing direct separation of the two processes, even where the fragment kinetic energy is the same for both processes. The results for 45 and 135 fs 790 nm pulses with an intensity of approximately 2.5 x 10(14) W/cm(2) differ from each other much more than one would expect from previous measurements with longer pulses. Ionization was negligible for the longer pulse and was strongly aligned along the laser polarization for the shorter pulse, but showed no structure in its kinetic energy distribution. In addition, the ionization to dissociation ratio was found to be much smaller than theoretically predicted for H(+)(2).     

Two- and three-body kinematical correlation in the dissociative recombination of H(3)(+)

Fragmentation patterns for dissociative recombination of the triatomic hydrogen molecular ion H(3)(+) in the vibrational ground state have been measured using the storage ring technique and molecular fragment imaging. A broad distribution of vibrational states in the H(2) fragment after two-body dissociation and a large predominance of nearly linear momentum geometries after three-body dissociation are found. The fragmentation results are directly contrasted with Coulomb explosion imaging data on the initial H(3)(+) geometry, compared to existing wave-packet calculations, and considered in the light of a simple physical picture.     

Controlling HD+ and H+2 dissociation with the carrier-envelope phase difference of an intense ultrashort laser pulse

Carrier-envelope phase difference effects in the dissociation of the HD+ molecular ion in the field of an intense, linearly polarized, ultrashort laser pulse are studied in the framework of the time-dependent Schr?dinger equation. We consider a reduced-dimensionality model in which the nuclei are free to vibrate along the field polarization and the electrons move in two dimensions. The laser has a central wavelength of 790 nm and a pulse length of 10 fs with intensities in the range 6x10(14) to 9x10(14) W/cm(2). We find that the angular distribution of dissociation to p+D and H+d can be controlled by varying the phase difference, generating differences between the dissociation channels of more than a factor of 2. Moreover, the asymmetry is nearly as large for H+2 dissociation.     

Electron localization of linear symmetric molecular ion H_3~(2+)

Electron localization in the dissociation of the symmetric linear molecular ion H_3~(2+) is investigated. The numerical simulation shows that the electron localization distribution is dependent on the central frequency and peak electric field amplitude of the external ultrashort ultraviolet laser pulse. When the electrons of the ground state are excited onto the 2pσ~2Σ_u~+ by a one-photon process, most electrons of the dissociation states are localized at the protons on both sides symmetrically. Almost no electron is stabilized at the middle proton due to the odd symmetry of the wave function. With the increase of the frequency of the external ultraviolet laser pulse, the electron localization ratio of the middle proton increases, for more electrons of the ground state are excited onto the higher 3pσ~2Σ_u~+ ustate. 50.9% electrons of all the dissociation events can be captured by the middle Coulomb potential well through optimizing the central frequency and peak electric field amplitude of the ultraviolet laser pulse. Besides, a direct current(DC) electric field can be utilized to control the electron motions of the dissociation states after the excitation of an ultraviolet laser pulse, and 68.8% electrons of the dissociation states can be controlled into the middle proton.     

Coincident fragment detection in strong field photoionization and dissociation of H2

Electron-ion momentum spectroscopy is used to investigate the correlated electronic and nuclear motion in fragmentation of H2 in 4 x 10(14) W/cm(2), 25 fs laser pulses at 795 nm. Reaction channel dependent photoelectron spectra indicate that besides the main, stepwise H2 ionization H2(+) dissociation mechanism resulting in the products H(1s) + H(+) + e(-) a second new mechanism has to be assumed. The momentum distribution of H(+) ions in the dissociation channels H(1s) + H(+) + e(-) and 2H(+) + 2e(-) is found to be independent of the kinetic energy of the photoelectrons.     

Young-type interference in collisions between hydrogen molecular ions and helium

The dissociative electron transfer from He into 10 keV H2+ was measured in a kinematically complete experiment by using the cold target recoil ion momentum spectroscopy imaging technique in combination with a highly resolving molecular fragment imaging technique. The electron transfer into the dissociative b(3)Sigma+_(u) state of H2 could be selected by kinematic conditions. We find a striking double slit interference pattern in the transverse momentum transfer which we can modify by selecting different internuclear distances. Compared to an optical double slit, interference minima and maxima are interchanged. The latter is the result of a phase shift in the electronic part of the wave function.     

多周期激光相位对H2+谐波频移的影响

理论研究了多周期激光相位角对H2+谐波频移的影响。结果表明,在多周期激光驱动下H2+谐波光谱在零相位时呈现蓝移现象。随着激光相位增大,谐波光谱由蓝移转向红移。随着激光相位进一步增大,谐波红移减弱。理论分析表明谐波频移是由激光上升和下降区域谐波辐射强度变化引起的。并且谐波辐射强度变化对激光相位比较敏感。     

Enhanced electron–positron pair production by frequency chirping in one-and two-color laser pulse fields

Enhanced electron–positron pair production by frequency chirping in one- and two-color laser pulse fields is investigated by solving the quantum Vlasov equation. A small frequency chirp shifts the momentum spectrum along the momentum axis. The positive and negative frequency chirp parameters play the same role in increasing the pair number density. The sign change of the frequency chirp parameter at the moment t = 0 leads the pulse shape and momentum spectrum to be symmetric, and the number density to be increased. The number density of produced pairs in the two-color pulse field is much higher than that in the one-color pulse field and the larger frequency chirp pulse field dominates more strongly. In the two-color pulse fields, the relation between the frequency ratio of two colors and the number density is not sensitive to the parameters of small frequency chirp added in either a low frequency strong field or a high frequency weak field but sensitive to the parameters of large frequency chirp added in a high frequency weak field.     

An apparatus for studying momentum-resolved electron-impact dissociative and non-dissociative ionisation

A spectrometer for recoil ion momentum measurements has been built for studying electron impact ionisation and dissociation of molecules. The apparatus is described in detail, highlighting its capabilities, as well as differences in design from the ones already in use elsewhere. Momentum spectra of ions resulting from 1300 eV electron impact on CO₂ are presented. We observe a broad momentum distribution for the dissociative ionisation reaction leading to the formation of C⁺, and two momentum groups in the CO⁺ and O⁺ channel. By recording multiple ions arising from the same dissociative ionisation event, we also demonstrate the formation of fragment pairs O⁺:CO⁺, C⁺:O⁺, and O⁺:O⁺.     

Electron localization of H_2~+ in a dc electric field

A dc electric field is utilized to steer the electron motion after the molecular ion H_2~+ is excited by an ultrashort ultraviolet laser pulse. The numerical simulation shows that the electron localization distribution and the dissociation control ratio are dependent on the polarization direction and amplitude of the dc electric field. Most electrons of the dissociation state move opposite to the dc electric field and stabilize at the dressed-up potential well, for the dressed-down well is occupied by the electrons of the 1 sσ_g state.