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钒—硫团簇的形成和光解 总被引:2,自引:0,他引:2
报导了用激光直接溅射法产生钒硫团簇,并用串级飞行时间质谱仪研究了所产生的团簇离子的分布及紫外激光光解规律。钒硫二元团簇正负离子都是由周边硫原子包围团簇骨架而构成的,骨架是由数目大体相同的钒和硫原子组成,表示成(VS)n,它们结合紧密,构成了稳定的钒硫团簇的核心。稳定的团簇正离子为VnSn^+、VnSn^+^+和VnSn+2^+(n=1,2,…14)。VnSn^+团簇系列在n=2,4时具有很高的丰度 相似文献
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用多光子电离技术结合飞行时间质谱仪对氨与乙醇混合团簇进行了研究。在脉冲激光波长分别为266,355nm和532nm条件下,仅在355nm作用下观测到团簇离子。主要的电离产物为质子化的(C2H5OH)n(NH3)mH+(n=0—3,m=0—4)混合团簇离子,且各个序列的离子强度随m的增大而减小。经分析,氨与乙醇混合团簇电离后团簇离子发生内部质子化转移反应是形成质子化团簇离子的主要原因。不同尺寸团簇离子信号强度随电离激光光强变化的光强指数曲线显示,团簇均发生四光子电离过程。通过理论计算得到其中性和离子团簇的稳定结构,解离能,解离通道。并证实团簇发生电离解离时发生了团簇内质子转移反应。 相似文献
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第一性原理比较研究MnPm (M=Al, Ga, and In,2≤n+m≤3)团簇 总被引:1,自引:0,他引:1
利用密度泛函理论对MnPm (M=Al,Ga,and In)团簇的几何和电子结构性质及稳定性进行了研究。结果表明,三原子的MnPm团簇是二重态,而单体则是三重态。富P的MP2团簇是具有C2V对称性的等腰三角形结构,而富M的M2P团簇则是具有Cs对称性的三角形结构。在三原子磷化物团簇中,MP2团簇比M2P团簇稳定,而后者中M-P键的强度比前者强。对于这些小的磷化物团簇,电离势高于裂解能,表明裂解比电离占优势。 Ga2P比Al2P和In2P的HOMO-LUMO能隙和电离势都高,归咎于在富金属的M2P团簇中,相对较强的Ga-P键。 相似文献
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介绍了一种改进的反射式飞行时间质谱装置用于光解质量选择的团簇离子. 该装置中采用了\选质-减速-解离-再加速"的方式. 团簇离子在反射式飞行时间的一级聚焦点被选质,接着被减速,并且立即被光解,光解所产生的碎片以及没有被光解的母体离子被重新加速,这一系列过程都在靠近一级聚焦点的位置完成. 相对文献中报道的其他方式,采用这一方式更利于光解碎片和母体离子的分离,更容易确定光解激光的触发时间,同时,由于母体离子在一级聚焦点的空间分布比较窄,也有利于光解激光束照射到所有的团簇离子,从而提高光解效率. 对母体离子、碎 相似文献
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利用直接激光溅射族源的串接飞行时间质谱计,获得了磷原团族正离子Pn^+(n=4-25)与氮气的碰撞诱导离解质谱,分析了它们的碰撞解离规律,并由此对其团族离子Pn^+的结构特征和生长(成簇)过程进行推测。 相似文献
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利用密度泛函理论对MnPm (M=Al,Ga,and In,2≤n+m≤3)团簇的几何和电子结构性质及稳定性进行了研究.结果表明,三原子的MnPm团簇是二重态,而单体则是三重态.富P的MP2团簇是具有C2V对称性的等腰三角形结构,而富M的M2P团簇则是具有Cs对称性的三角形结构.在三原子磷化物团簇中,MP2团簇比M2P团簇稳定,而后者中M-P键的强度比前者强.对于这些小的磷化物团簇,电离势高于裂解能,表明裂解比电离占优势.Ga2P比Al2P和In2P的HOMO-LUMO能隙和电离势都高,归咎于在富金属的M2P团簇中,相对较强的Ga-P键. 相似文献
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利用激光溅射 分子束的技术 ,结合反射飞行时间质谱计 ,研究了Cu+、Ag+、Au+与乙硫醇的气相化学反应。结果显示这三种金属离子与 (CH3 CH2 SH) n 反应形成一系列团簇离子M+(CH3 CH2 SH) n,且团簇离子尺寸不一样。Ag+、Au+与乙硫醇的反应还生成了 (CH3 CH2 SH) +n ,由此推测Cu+、Ag+、Au+与乙硫醇团簇的反应存在两种通道 ,一种通道是生成M+(CH3 CH2 SH) n,另一种是生成 (CH3 CH2 SH) +n 。Cu+、Au+与乙硫醇的反应还生成了M+(H2 S) (M =Cu、Au) ,但是实验中没有观察到Ag+(H2 S) ,理论计算表明Ag+(H2 S)很不稳定。另外 ,分析产物离子M+(CH3 CH2 SH) n 的强度发现 ,n =1~ 2之间存在明显的强度突变现象 相似文献
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利用激光溅射-分子束的技术,结合反射飞行时间质谱计,研究了Cu+、Ag+、Au+与乙硫醇的气相化学反应.结果显示这三种金属离子与(CH3CH2SH)n反应形成一系列团簇离子M+(CH3CH2SH)n,且团簇离子尺寸不一样.Ag+、Au+与乙硫醇的反应还生成了(CH3CH2SH)+n,由此推测Cu+、Ag+、Au+与乙硫醇团簇的反应存在两种通道,一种通道是生成M+(CH3CH2SH)n,另一种是生成(CH3CH2SH)+n.Cu+、Au+与乙硫醇的反应还生成了M+(H2S)(M=Cu、Au),但是实验中没有观察到Ag+(H2S),理论计算表明Ag+(H2S)很不稳定.另外,分析产物离子M+(CH3CH2SH)n的强度发现,n=1~2之间存在明显的强度突变现象. 相似文献
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The fabrication method and the pyroelectric response of a single element infrared sensor based lead zirconate titanate (PZT) particles and polyvinylidene fluoride P(VDF-TrFE) copolymer composite thick film is reported in this paper. A special thermal insulation structure, including polyimide (PI) thermal insulation layer and thermal insulation tanks, was used in this device. The thermal insulation tanks were fabricated by laser micro-etching technique. Voltage responsivity (RV), noise voltage (Vnoise), noise equivalent power (NEP), and detectivity (D*) of the PZT/P(VDF-TrFE) based infrared sensor are 1.2 × 103 V/W, 1.25 × 10−6 V Hz1/2, 1.1 × 10−9 W and 1.9 × 108 cm Hz1/2 W−1 at 137.3 Hz modulation frequency, respectively. The thermal time constant of the infrared sensor τT was about 15 ms. The results demonstrate that the composite infrared sensor show a high detectivity at high chopper frequency, which is an essential advantage in infrared detectors and some other devices. 相似文献
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Evgenij Zubko Reiko Furusho Tetsuo Yamamoto Gorden Videen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(11):1848-1863
We present multispectral photo-polarimetric observations of comet 17P/Holmes taken at three different dates. These observations show the evolution of the negative polarization branch (NPB) as a function of time and wavelength. We perform discrete-dipole approximation (DDA) simulations on agglomerated debris particles of various sizes and refractive indices. Our simulations show that the observations are consistent with the cloud being composed of agglomerated debris particles having refractive indices of approximately m=1.5-1.6+0.1i. Our results are also consistent with the particles obeying a power-law size distribution r-a and having a lower particle-radius cut-off of approximately 0.6 μm, where the index a∼3.5 for the early observations and shrinks to a∼1.5 for the later observations. This is consistent with the smaller, more accelerated particles in the distribution being propelled out of the field of view. 相似文献
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第一原理对Aln040234.gif (202 bytes)(n+m=5)团簇结构和稳定性研究 总被引:4,自引:3,他引:1
用第一原理中的B3LYP和MP2方法,在6-311G水平上对AlnP- m(n+m=5)的各种可能构型进行几何构型优化,预测各团簇的稳定结构,从中得出各个团簇稳定构型之间的基本关系,当n>m时,团簇的稳定构型与Al-n相似, 而当n< m时,团簇的稳定构型与P-m相似.并用B3LYP/6-311G方法计算了AlnP -m的垂直电子离能(VDE)和绝热电子离解能(ADE),同实验数据符合的较好. 相似文献
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第一原理对AlnP-m(n+m=5)团簇结构和稳定性研究 总被引:6,自引:6,他引:0
用第一原理中的B3LYP和MP2方法,在6-311G^*水平上对AlnPm^-(n+m=5)的各种可能构型进行几何构型优化,预测各团簇的稳定结构,从中得出各个团簇稳定构型之间的基本关系,当n>m研时,团簇的稳定构型与Alm^-相似,而当n<m时,团簇的稳定构型与Pm^相似。并用B3LYP/6—311G。方法计算了AlnPm^-的垂直电子离能(VDE)和绝热电子离解能(ADE),同实验数据符合的较好。 相似文献
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Gholam Reza Gordani Reza ShojaRazavi Sayed Hamid Hashemi Ali Reza Nasr Isfahani 《Optics and Lasers in Engineering》2008,46(7):550-557
Laser surface alloying of an electroless plating Ni–P coatings on an Al-356 aluminium alloy was carried out using a 1-kW pulsed Nd:YAG laser. The microstructure, chemical composition and phase identification of the alloyed layer were determined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD), respectively. It was shown that laser surface treatment produced a relatively smooth, crack-free and hard surface layer. The hardness of the surface significantly increased due to the formation of the uniformly distributed fine Ni–Al intermetallic phases. The corrosion behaviour of the surface alloyed specimens in 3.5% NaCl solution at 23 °C was also determined by electrochemical techniques. The laser-alloyed surface showed an improved corrosion and pitting potential compared to the substrate as well as the plated Ni–P coating. 相似文献
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Avdievich NI Hetherington HP 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,186(2):341-346
Typically 31P in vivo magnetic resonance spectroscopic studies are limited by SNR considerations. Although phased arrays can improve the SNR; to date 31P phased arrays for high-field systems have not been combined with 31P volume transmit coils. Additionally, to provide anatomical reference for the 31P studies, without removal of the coil or patient from the magnet, double-tuning (31P/1H) of the volume coil is required. In this work we describe a series of methods for active detuning and decoupling enabling use of phased arrays with double-tuned volume coils. To demonstrate these principles we have built and characterized an actively detuneable 31P/1H TEM volume transmit/four-channel 31P phased array for 4 T magnetic resonance spectroscopic imaging (MRSI) of the human brain. The coil can be used either in volume-transmit/array-receive mode or in TEM transmit/receive mode with the array detuned. Threefold SNR improvement was obtained at the periphery of the brain using the phased array as compared to the volume coil. 相似文献
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The present work reports a simple method to produce the aluminum superhydrophobic surface based on an interface reaction between an aluminum foil and zinc aqueous solution. The products were characterized by field-emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectrum. The field-emission scanning electron microscopy images show that the coating surface is composed of micro/nanoscale binary structure, which is similar to the structure of lotus leaf. The wettability of the coating surface was also investigated. It was found that after treatment with stearic acid, the wettability of the aluminum foil changed from superhydrophilic to water-repellent superhydrophobic. The complex micro/nanoscale binary structures along with the low surface energy lead to the high surface superhydrophobicity. 相似文献
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Grigor L. Georgiev Taslema Sultana Ronald J. Baird Golam Newaz Rahul Patwa 《Applied Surface Science》2008,254(22):7173-7177
KaptonFN film consists of a polyimide core that has been laminated with FEP fluoropolymer outer layers. This composite material's resistance to most chemical solvents, heat sealability and low moisture uptake make KaptonFN attractive as a packaging material for electronics and implantable devices. KaptonFN/Ti micro-joints were fabricated by using focused infrared laser irradiation. The micro-joints were mechanically debonded, and the KaptonFN/Ti interfaces were studied by using X-ray photoelectron spectroscopy (XPS). The locus of failure of the joints was found to be in the FEP layer near the interface with the Ti. The XPS results give evidence for the formation of TiF bond in the interfacial region. 相似文献