铜硫团簇离子的形成与光解

本文首次报导用激光溅射方法产生了铜硫团簇离子Cll。S：，并对其进行了紫外激光解离，得出了团簇离子的组成及光解规律．与以前关于过渡金属与非金属的二元团簇研究结果［‘－‘］有所不同，铜是具有满壳层d电子结构的过渡金属元素，这使得无论是所产生的团簇的组份，还是其光解规律，都表现出了明显的特点．本文在分析铜硫团簇离子的形成和光解规律的基础上，初步讨论了团簇的结构特征以及过渡金属满壳层d电子结构对团簇的形成与结构的影响．实验是在本实验室自制的串级飞行时间质谱仪上进行的，有关仪器的详情参见文献问．所用样品为：…     

铜/硒二元团簇离子的形成和紫外光解

用串级飞行时间质谱仪结合激光直接溅射的方法产生了铜/硒二元团簇正负离子,正离子主要系列为(Cu₂Se)_nCu⁺和(Cu₂Se)_n⁺,负离子主要系列为(Cu₂Se)_nCuSe^-和(Cu₂Se)_nSe^-;研究了团簇正离子的紫外光解.结果表明,光解产物主要是一级谱中丰度较大的一些离子.用密度泛函方法(DFT)对Cu₃Se^-,Cu₃Se₂⁺的稳定构型及光解通道进行了理论计算,解释了实验中观察到的现象.     

铁-硒二元团簇离子的产生和紫外光解

用激光直接溅射的方法产生了铁-硒二元团簇,并用串级飞行时间质谱仪研究了二元团簇的组份和光解规律。一级谱中组成FenSen+、FenSen-1+和FenSen-、FenSen+1-是二元团簇的结构骨架和稳定组份。团簇正离子FenSen+的紫外光解结果表明,光解产物主要为一级谱中丰度较大的离子。用密度泛函方法（DFT）优化了Fe2Se2+的几何结构,并计算了其光解通道,能较好地解释光解的实验结果。     

氰化钾团簇的结构和形成机理研究

利用激光气化铁氰化钾或亚铁氰化钾并利用飞行时间质谱检测方法对氰化钾团簇的形成机理进行了研究，结果发现：团簇正离子可归属为［Ｋ（ＫＣＮ）＿ｎ］￣＋，ｎ＝０～３７，它们的幻数为ｎ＝４、１３、２２、３７；团族负离子可归属为［（ＫＣＮ）＿ｎＣＮ］￣－＝，ｎ＝０～１３，它们的幻数为ｎ＝４、１３。这些幻数与氯化钠等碱金属卤化物团簇体系完全一致。这表明：它们的团簇结构应该是相同的，即１×３×３（ｎ＝４）、３×３×３（ｎ＝１３）、３×３×５（ｎ＝２２）、３×５×５（ｎ＝３７）结构。因此氰化钾晶体的初期形成过程也应采取ＮａＣｌ型结构的增长途径。在激光气化产生的等离子体中，正、负离子与中性团簇的碰撞增长反应、正离子与负离子的复合反应以及团簇的亚稳态解离反应造成了团簇离子的不同丰度分布。氰化钾团簇中稳定立方体结构的产生决定了幻数的出现。     

银硫团簇离子的形成与光解

银硫团簇离子的形成与光解于忠德，高振，张南，朱起鹤，孔繁敖（中国科学院化学研究所分子反应动力学国家重点实验室，北京１０００８０）本文首次报道用激光溅射方法产生了银硫团簇离子，并研究了部分团簇离子的紫外激光解离规律。由于银与铜都是具有满壳层ｄ电子结构的...     

锗分族元素二元团簇及其与Co形成的团簇离子

通过比较激光烧蚀E1/E2 (代表Ge/Sn， Ge/Pb和Sn/Pb) 和Co/E (E为Ge、Sn、Pb)混合样品形成的二元团簇负离子飞行时间质谱分布和谱峰的相对强度及形成的幻数团簇离子峰，发现E1/E2二元团簇离子中原子量大的锗分族元素在团簇离子中占主要组分，而原子量小的元素则少量掺杂，其组成和分布特点说明其结构和性质与纯E团簇离子相似，可能的结构为该类负离子团簇所有原子都在笼结构的骨架上；对于二元团簇离子GeSn9－、GePb9－和SnPb9－其结构可能是双帽反四棱柱构型，只是每个原子均为骨架的一部分.而对激光烧蚀过渡金属钴与锗分族元素的混合物的研究发现，反应形成了丰富的Co/E二元合金团簇负离子，分析发现该类簇离子为钴内包覆于E(锗分族元素)笼状结构.幻数离子CoGe10－、CoSn10－和CoPb10－可能具有双帽四角反棱柱结构，而CoPb12－可能具有二十面体构型，钴原子均为笼状结构的中心.     

幻数团簇离子Mn+5

Magic number cluster ion Mn5+ and abundant Mn/O cluster ions havc been formed by 532nm laser ablation of MnCO3 solid sample with time-of-flight mass spectroscopy detection. The experimental results show that Mn5+ was formed in the cooler dilute tail region of the plume produced by laser ablation, while Mn/O cluster ions were mainly formed in the hotter dense preceding portion of the plume, they all were produced by postablation cluster growth in the ablation plume. Pentagonal with D(5h) symmetry is the possible structure of Mn5+, which is supported by our ab initio calculation.     

碳原子和离子团簇奇偶性的研究

本文用Huckel-Hubbard方法,考虑多电子体系的组态相互作用,计算出线性碳原子和离子团簇(Gn,C_n~±)的π电子体系能量E_n。两相邻原子簇的能量差△E_N=|E_n-E_(n-1)|与n的关系显示出与实验相符合的奇偶性质。由于条件的限制,只计算到n为6的碳原子和离子团簇,然后利用电子结构图,外推出n为7和8的原子和离子团簇的π电子能量。所得结果也定性显示出团簇的奇偶性。此外,我们还利用D_v—X_α方法进行对比计算,并讨论了计算结果。     

激光蒸发产生钽钌酸铅团簇负离子的研究

激光蒸发产生钽钌酸铅团簇负离子的研究巨新，杨建红，施朝淑，张南，高振，孔繁敖，朱起鹤（中国科学技术大学，合肥，２３００２６）（中国科学院化学研究所，北京）关键词团簇离子，激光蒸发，奇偶性厚膜电阻以ＲｕＯ２、Ｐｂ２Ｒｕ２Ｏ７或Ｂｉ２Ｒｕ２Ｏ７作导电相，...     

新团簇形成的动力学研究

利用紧束缚模型,通过对不同初始条件下的碱金属团簇的碰撞研究,得到形成大分子团簇的可能性.结果表明,对同一种团簇,具有空间对称性的团簇间的碰撞更易形成大团簇,而平面结构的团簇碰撞则反之,并且空间结构的团簇碰撞形成的新团簇复合体更加稳定.另一方面,团簇碰撞过程是可逆的.     

碳氮二元簇离子的激光产生与碰撞诱导解离研究

以脉冲激光束在高真空中溅射铁氰化钾,产生了各种组成的碳氮原子簇负离子,记录了它们的飞行时间质谱。根据这些簇离子的碰撞诱导解离研究结果,推测了它们的结构,发现它们大都具有超共轭的稳定体系,它们的构型随成簇氮原子数的增加,从一维直链向二维芳环转化。     

激光作用产生的CnH^-、CnF^-、CnF3^-及其结构分析

作者在自制的仪器上, 以脉冲激光(波长532nm, 能量密度10^8W/cm^2)在10^-^4Pa的真空中溅射合适的样品, 产生了一系列CnH^-、CnF^-和CnF3^-, 记录了它们的飞行时间质谱。     

Bare phosphorus and binary phosphide cluster ions generated by laser ablation

Both positive and negative phosphorus cluster ions were generated from the laser ablation of a red phosphorus sample. The mass distribution of phosphorus cluster ions was found to be very sensitive to the power density of the ablation laser. The P ₇ ⁺ species exhibits the highest signal intensity in the recorded mass spectra of bare phosphorus cluster cations, as does P ₅ ^- among the anions. Their special structural stability can be attributed to their planar configuration and their aromatic character. As the phosphorus cluster size increases, the odd/even alternation of the signal intensity becomes more pronounced. For the P _n ⁺ species with n > 24, the relative abundance varies in the order of 8 and P _n ⁺ with n = 8k + 1 (k = 3–11) are more intense than their neighbors. For comparison, some binary phosphide cluster ions, including C_nP _m ^- , Si_nP _m ^- , B_nP _m ⁺ and Al_nP _m ⁺ , were produced as well. The mass distribution of binary phosphide cluster ions changes with different components. From analysis of the recorded mass spectra of the phosphide cluster ions, the larger clusters may be in a polyhedral configuration and tend to have all valence electrons paired.     

FTMS studies of mass-selected,large cluster ions produced by direct laser vaporization

A method is described for the production of large cluster ions by direct laser vaporization in a low-pressure FTMS. Production of high-mass carbon cluster ions (C_n⁺; 40 <n < 180) and bismuth-antimony (Bi_xSb_y⁺) cluster ions containing up to five metal atoms are reported. The observed distributions are compared with those obtained previously by both direct laser vaporization and molecular beam sources. Details of the mechanism for formation of these larger cluster ions by direct laser vaporization are discussed. The mass selectivity and long ion residence times obtainable in the FTMS may now be utilized in the study of these cluster ions. Results are presented from a limited study of the ion/molecule reactions and collision induced dissociation of the high-mass carbon cluster ions.     

A comparative study of the polyaniline thin films produced by the cluster beam deposition and laser ablation methods

Polyaniline (PANI) thin films have been prepared by applying the novel neutral and ionized cluster beam deposition (NCBD and ICBD) methods and the pulsed laser deposition (PLD) technique to the PANI samples of half-oxidized emeraldine base (EB-PANI) and protoemeraldine base forms in a high-vacuum condition. Characterization of the oxidation states and structural changes of pristine and doped thin films has been performed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and x-ray photoelectron spectroscopy. Spectroscopic measurements demonstrate that the dominant structure of NCBD and ICBD thin films corresponds to the reduced leucoemeraldine base state, whereas the chemical composition of PLD thin films depends critically on the laser fluence and the molecular weight of PANI target. The congruent deposition is only obtained for the PLD films deposited by the laser-induced decomposition of the low-molecular-weight targets in the low to intermediate fluence regime (below 100 mJ/cm2 with a pulse duration of 7 ns). The surface morphology examined by atomic force microscopy measurements shows that the cluster and laser beams are effective in producing smooth, uniform polymeric thin films. After I2 and HCl doping, the electrical conductivities of the NCBD, ICBD, and particularly PLD thin films are increased significantly. The higher conductivity of PLD films is ascribed to higher amounts of quinoid di-imine doping sites in the EB-PANI state, and the overall structure-conductivity characteristics are consistent with the spectroscopic observations.     

Studies of Sb and Bi cluster produced by laser desorption

Direct production of cations and anions of metal clusters of Sb and Bi by laser evaporation in a vacuum has been studied. Bulk sample substrates are irradiated by 1064, 532 and 355 nm beams at variable intensity, and the ions produced are accelerated and identified by time-of-flight mass spectrometry. At 1064 nm, the cation distributions show that Sb ₃ ⁺ and Bi ₃ ⁺ are the most abundant species, while the monomer and dimer cations are almost non-existent. The anion spectra indicate very low yields of Sb^? and Bi^? with dominant dimer anion species. These patterns persist with laser power variation within the stable operation domain. With lower incident laser wavelength, the mass distributions are modified, favouring the production of the light cluster ions. In no circumstances were Sb and Bi ions withn>5 observed. Many of the observed phenomena can be explained if one assumes that for these elements, clusters withn<6 are formed on the substrate surface. Cluster ions are produced via a prompt desorption process, and are subjected to photon induced reactions due to the same incident laser beam. However, more detailed investigation of the desorption properties will be necessary to confirm such a desorption mechanism.     

Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M=Ba,Sr, Ca,Mg)

Laser ablation of YMCuO metal-composite-oxides (M=Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa₂Cu₃O_7?x (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed.     

Plasmon profiles and shapes of sodium cluster ions

Photo-absorption cross-sections for charged sodium clusters (14 to 48 atoms) have been measured for photon energies from 2.0 eV to 3.5 eV. The spectra are dominated by surface plasma oscillations of the valence electrons exhausting 70–100% of the dipole sum rule. The mean resonance energy of ?2.75 eV is nearly independent of cluster size. A splitting of the resonance peaks is observed for non-“magic” clusters and discussed in terms of a deformation picture involving prolate and oblate shapes.     

Metal particles produced by laser ablation for ICP-MS measurements

Pulsed laser ablation (266 nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm⁻². Characterization of particles and correlation with inductively coupled plasma mass spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of ∼50 and ∼12 for fs versus ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the ⁶⁶Zn transient signal by a factor of 10 compared to nanosecond laser pulses.