紫外激光和压力共同作用下C60-peapod的聚合相变研究

采用气相扩散方法将C₆₀分子填充到单壁碳纳米管(SWNTs)中，制备出高填充比率的豆荚形纳米材料C₆₀@SWNT，又称为peapod.用金刚石对顶砧(DAC)装置获得高压，在高压下同时利用紫外激光处理样品，通过激光和压力的共同作用研究了C₆₀分子在碳管内的聚合相变.在21.5GPa高压下，同时紫外激光(325nm)照射30min后，拉曼光谱表明C₆₀分子在碳管内发生了聚合，形成一维链状O相聚合结构，且该相变是不可逆的. 关键词： 60 peapod')" href="#">C₆₀ peapod 紫外激光 高压 拉曼光谱     

C74分子光谱特性及电子结构的密度泛函研究

利用第一性原理的密度泛函理论和非平衡格林函数的方法研究了C₇₄分子的分子轨道密度、振动光谱和态密度.结果显示C₇₄分子的能隙不足0.6 eV.比较C₇₄分子的电子云分布发现,在HOMO和LUMO状态下的电子只分布在C₇₄分子的半球表面侧,电子在成键过程中都表现出了较好的离域特性.C₇₄分子的红外光谱和拉曼光谱显示,碳碳键的振动在有些频率处只有红外活性,有些频率处只有拉曼活性,还有一些频率处既有红外又有拉曼活性.另外,考虑电子自旋作用时C₇₄分子态密度的极大值数量有所增加,并使简并的能级发生分裂.     

掺杂C60的SiO2气凝胶的制备及荧光特性研究

利用“化学掺杂”方法，制备掺杂C₆₀-SiO₂气凝胶，对掺杂C₆₀-SiO₂气凝胶的红外吸收光谱、飞行时间质谱的测试表明C₆₀分子被成功地掺入SiO₂气凝胶中．室温条件下，在Ar⁺激光（488nm）激发下，观察到掺杂C₆₀-SiO₂气凝胶有很强的可见发光现象，发光峰位较纯C₆₀发光明显蓝移 关键词：     

C60薄膜的离子注入损伤研究

在200 keV重离子加速器上，用120—360 keV的H,N,Ar和Mo离子注入C₆₀薄膜．对注入后薄膜的拉曼谱进行了分析．结果表明，不同离子注入C₆₀薄膜后，C₆₀的1469 cm^-1特征峰随注入剂量的增加均呈指数式下降，同时在1300—1700 cm^-1范围出现非晶碳峰，并逐渐增强，最终完全非晶化．而且1469 cm^-1拉曼峰的强度及C₆₀薄膜完全非晶化所对应的剂量与注入离子的种类和能量有关．进一步的分析表明，C₆₀分子的损伤主要是由注入离子的核能量转移所造成，与电子能量转移无关．H离子注入C₆₀薄膜后，1469 cm^-1处特征拉曼峰向短波方向非对称展宽，这可能是注入的H离子通过电子能量转移使C₆₀分子发生聚合的结果. 关键词：     

C60分子电子激发态结构的理论研究

C₆₀分子有较丰富的分子键轨道,同时C₆₀分子离子是稳定存在的,因此预期C₆₀分子的里德伯轨道也是稳定存在的。本文在独立电子近似的基础上,应用多重散射自洽场方法,从理论上统一自洽地探讨了C₆₀分子的分子键轨道和分子里德伯轨道的能级结构。这些轨道能级结构在独立电子近似的层次上模拟了C₆₀分子的电子结构。所得结果和已有的理论和实验结果进行了比较和分析,说明本文结果是自洽合理的,并和已有的实验值符合良好 关键词：     

竹红菌乙素(HB)在C60与三乙胺分子间电子转移反应中的光催化作用

用ESR方法探讨了在C₆₀与三乙胺(Et₃ N)的分子间电子转移反应中竹红菌乙素(HB)的光催化作用.通过对Et₃N/C₆₀/HB电子转移反应体系及其中间体的研究得知:在HB存在的条件下,可通过光催化电子转移反应机理,实现室温下由Et₃N到基态C₆₀的分子间电子转移     

高压低温下固体C60中的取向有序态及再取向的弛豫行为

通过构造C₆₀分子间的相互作用，研究了高压下及玻璃化转变温度附近固体C₆₀的取向状态占有概率分布及再取向的弛豫行为，所得结论均能较好地解释热导率实验中的异常现象. 关键词：     

密度泛函理论计算内掺氢分子富勒烯H2＠C60及其二聚体的几何结构和电子结构

采用密度泛函理论中的广义梯度近似(generalized gradient approximation,简称GGA),对内掺氢分子富勒烯H₂＠C₆₀及其二聚体的几何结构和电子结构进行了计算研究.发现无论是在H₂＠C₆₀单体,还是在其二聚体中,氢倾向以分子形式存在于碳笼中心处,且在室温下氢分子可以做自由旋转.电子结构分析表明,氢分子掺入到C₆₀和C₁₂₀中,仅对距离费米能级以下-8eV至-5eV能级处有一定的贡献,其他能级的分布和能隙几乎没有变化. 关键词： 几何结构 电子结构 密度泛函     

Raman光谱方法研究三氯甲烷与苯分子间的C/H…π相互作用

测量了不同浓度三氯甲烷（CHCl₃）与苯（C₆H₆）二元溶液的Raman光谱,随C₆H₆浓度的增加,受分子间C/H…π相互作用的影响,CHCl₃中C—H键伸缩振动频率向低波数移动;当CHCl₃体积分数小于40%,C—H键伸缩振动频率不变,分子间C/H…π相互作用达到饱和.分别以CHCl₃和C₆H₆体积分数为70%的CHCl₃-C₆H₆混合溶液为研究对象,测量了它们的高压和低温Raman光谱.根据CHCl₃中C—H键伸缩振动频率随压强和温度的变化关系,得出了分子间C/H…π相互作用对压强和温度的扰动表现出不稳定性.     

碳分子线C5在激光场中的含时密度泛函理论研究

运用含时密度泛函理论和分子动力学相结合的方法, 研究了C₅分子线在强激光场中的电离激发.研究发现, 当考虑激光强度对C₅分子线激发的影响时, 激光强度越强, 分子吸收的能量越多, 电离也越早, 最终电离的电子也越多, 而且沿激光极化方向的偶极矩的变化及峰值也越大. 关于激光极化方向对C₅分子线激发的影响的研究表明, 当激光极化方向沿着C₅分子线轴向时, 分子的电离大大增强, x方向的激光脉冲仅能激发起x方向的偶极振荡, 而y方向的激光脉冲仅能激发起y方向的偶极振荡, 而且x方向的激光脉冲激发的偶极振荡强. 研究还表明, 当激光极化方向沿着C₅分子线轴向时, 尽管由于电离增强而导致C₅分子线C–C键振动的同步性变差, 但在两种激光极化方向情况下, C₅分子线的振动模式与中性C₅分子线的振动模式相同. 关键词： 含时密度泛函理论 分子动力学 分子电离 碳分子线     

C60三阶微商吸收光谱分析

利用三阶微商吸收光谱观测到了紫外一可见区Ｃ６０更为丰富捐收跃迁结构，基于 伦兹线型假设，实验上拟合确定了相应迁能量和寿命加宽参数，并对跃迁结构进行了初步指认，给出了部分振动模的频率。与常规吸收光谱比较，表明了三阶微商光谱是分析Ｃ６０等团簇光物理特性的有效手段。     

外电场作用下Si_2O分子的激发特性

主要对2种Si2O分子异构体的激发特性进行研究,由计算结果可知,外电场对Si2O分子的激发能,振子强度,跃迁偶极矩及吸收光谱有着显著的影响.无外电场时三角型Si2O(C2v,1A1)分子在可见光区无吸收谱,外电场作用下其在可见光区(407.18—526.93nm)有比较弱的吸收谱.直线型Si-Si-O(C∞v,3Σ-)分子在有无外电场作用时在蓝光和紫光区均有一定的吸收谱,其中比较难得的是在蓝色光区(478.88—488.59nm)呈现较强的吸收谱.     

Electronic structure and spectra of N-methylfullerenepyrrolidine

A quantum-chemical analysis of the donor-acceptor properties of a C₆₀ + dimethylenemethylamine binary system is performed. It is shown that the term of the intermolecular interaction is two-well, because of which the optimization of the system structure at the initial distances between the molecules of 0.21 nm or smaller leads to the formation of N-methylfullerenepyrrolidine C₆₀. At initial distances exceeding 0.25 nm, a weakly bound charge transfer complex with almost complete retention of the properties of the individual molecules is formed. The low-temperature emission and absorption vibronic spectra of N-methylfullerenepyrrolidine C₆₀ in the crystalline toluene matrix are studied experimentally. It is found that the absorption spectra of the fulleroid and pure fullerene in the region corresponding to the excitation of the lowest electronic states are generally similar. The difference observed between the low-frequency spectra agrees completely with the quantum-chemical analysis performed.     

FT visible absorption spectroscopy of porphine in noble gas matrices

Polarized visible absorption spectra of free-base porphine photo-oriented in noble gas matrices were observed by Fourier-transform spectroscopy. The symmetries of over 60 vibronic transitions in the Q_x region and about 20 in the Q_y region were assigned and the symmetric N---H stretching vibration in the Q_x state was identified (3386 and 3392 cm⁻¹ in the two sites in xenon matrix).     

Some features of analysis of solutions of fullerenes C60 and C70 by their absorption spectra

The absorption spectra of a series of solutions of C₆₀ and C₇₀ and of their mixture in o-xylene are studied. The deviation from the Bouguer-Lambert-Beer law was observed in the UV absorption band of the solutions. The possible reasons for this effect were analyzed. It is shown that to calculate reliably the composition and concentrations of fullerene mixtures, it is necessary to determine preliminarily the linearity region for the 335-nm absorption band.     

The vacuum ultraviolet spectra of HCN,C2N2, and CH3CN

Quantitative vacuum ultraviolet absorption spectra for HCN, C₂N₂, and CH₃CN have been obtained over the wavelength range 60 nm ? λ ? 160 nm. Where comparison is possible, our measurements of the absorption coefficients for HCN and C₂N₂ are consistent with previous studies. Because of the superior resolution of this work (0.05 nm), vibrational assignments in the valence and Rydberg transitions of HCN have been extended while higher members of the Rydberg series in CH₃CN have been identified.     

Theory of two-phonon absorption processes in liquid paraffins

Calculated absorption spectra are given for linear C₈H₁₈, C₁₀H₂₂, C₁₆H₃₄ and C₂₀H₄₂ chains, based on the assumption of a two-phonon absorption mechanism. In the present work the normal modes of vibration of different finite chains are computed directly, without recourse to the Pitzer sampling approximation and without the assumption of strict k-selection rules. The calculated spectra are found to be much more sensitive to chain length than the experimental spectra. A possible explanation of the relative insensitivity of the observed spectra is suggested in terms of a characteristic chain segment length common to all the chains. Ironically, the apparent importance of chain segmentation in the two-phonon absorption suggests that one-phonon transitions may also play a significant rôle in the absorption process.     

Crystal growth, spectroscopy, and diode pumped laser performance of Pr,?Mg:SrAl12O19

Polarization dependent ground state absorption, excited state absorption and emission cross sections of Pr,?Mg:SrAl₁₂O₁₉ are determined in the visible and ultraviolet spectral region. It is shown that excited state absorption to the 4f5d configuration does neither occur on the pump wavelength in the blue region nor on any of the visible laser transitions. Efficient laser action at 643.5?nm is demonstrated with slope efficiencies of up to 47% with respect to the absorbed pump power. Output powers up to 75?mW are achieved by pumping with an InGaN laser diode at 444?nm.