不同溶剂中硝基苯胺分子非线性光学性质的研究

在含时密度泛函理论水平上研究了溶剂对硝基苯胺分子非线性光学性质的影响 .溶剂效应通过极化连续模型来研究 .首先采用极化连续模型在密度泛函理论水平上优化了硝基苯胺分子在溶剂中的几何结构 ,从而研究了溶剂引起硝基苯胺分子几何结构的变化 .然后采用极化连续模型在含时密度泛函理论水平上计算了不同溶剂中硝基苯胺分子的激发态能量和电偶极矩 ,并利用两态模型首次给出了不同溶剂中二次谐波振荡过程的一阶非线性超极化率的色散关系 .计算结果表明 ,极性溶剂对硝基苯胺分子的非线性光学性质有较大的影响 .在低的辐射场频率下 ,理论给出的一阶非线性超极化率的色散关系和实验结果符合得较好 .最后对所得结果从理论上给出了可能的解释并讨论了两态模型的可靠性 .     

二维电荷转移分子非线性光学性质的理论研究

运用密度泛函理论B3LYP方法在6-31+G（d,p）水平上计算了11个X型二维电荷转移分子的电荷分布、紫外吸收光谱、第一超极化率.结果表明：在x或y方向延长共轭体系,最大吸收波长 红移,第一超极化率 增大,并且在y方向延长共轭体系,能够较好的优化分子透明性与分子非线性光学性质,获得兼具大 和良好透光性的非线性光学性能好的分子;另外,杂原子N取代芳香环上的C原子的位置和数目对分子非线性光学性质有重要影响.     

氢键对于偶氮苯衍生物非线性光学性质的影响

设计合成了三种偶氮苯化合物,分子的一端为羟基,改变其对位取代基团硝基、氢和甲氧基. 并利用Z扫描技术分别测试了偶氮苯化合物在THF及CHCl₃溶液中的三阶非线性光学响应,所用激光输出波长为532 nm、脉宽为16 ns. 结果表明：对于不同取代基团的偶氮苯化合物,改变不同溶剂其酚羟基与THF 溶剂分子间形成了氢键,体系中供电子能力增强,分子排列有序度提高,因此非线性吸收系数和非线性折射率)相比较于CHCl₃溶液,均表现出了不同程度的增强;同一溶剂中,4-硝基-4'-羟基偶氮苯由于其形成了推拉电子结构,电子云更易于流动,电荷转移程度高,表现出更大的非线性光学响应特性.     

4-N-甲基苯乙烯砒啶盐衍生物非线性光学性质的理论研究

设计了9种4-N-甲基苯乙烯砒啶盐衍生物分子,以密度泛函B3LYP/6-31G方法优化的构型为基础,采用耦合微扰(CPHF)方法研究了体系的非线性光学性质,对体系的电荷布居、吸收光谱及前线分子轨道等性质进行了分析,发现用线性关系对各分子一阶静态超极化率、基态和激发态偶极矩差、激发能及取代基给电子能力之间的关系进行描述是可行的,而且该分子体系的非线性光学响应完全可用二能级模型近似处理.     

溶剂中一、二维电荷转移分子二阶非线性光学性质理论研究

以典型的一、二维电荷转移分子,对硝基苯胺(pNA),1,3-二氨基-4,6-二硝基苯(DADB)分子为例,运用密度泛函理论(DFT)B3LYP和含时耦合微扰(TDHF)方法在6-31+G(d,p)水平上研究了溶剂和入射光频率对目标分子的非线性光学性质的影响.研究发现溶剂分子对分子一阶超极化率β和紫外吸收光谱的影响很大,但对一阶超极化率各向异性比η和退偏比D的影响很小,这是由于随着溶剂相对介电常数的增加,一阶超极化率的分量︱βxxy︱和︱βyyy︱不断增加,且二者具有很好的线性相关性.然而,考虑色散效应后,不同溶剂中分子的一阶超极化率及其各向异性参数都不相同,色散效应对分子一阶超极化率及其各向异性性质均有很大影响.考虑溶剂效应和色散效应后得到的计算结果与实验结果符合得较好.     

电场调控的碳纳米管非线性光学开关及其管径效应

本文借助密度泛函理论方法获得了五个不同管径碳纳米管在外电场作用下的最优几何结构和相应的性质,研究了外电场对碳纳米管的结构和性质的调控作用.结果表明外电场导致了碳纳米管内部的电荷转移,引起了碳纳米管第一超极化率(β₀)的急剧增大.例如CNT(6, 3),当电场从0增大到工作电场F_w=80×10^-4 au时,碳纳米管的β₀值从0 au可增大到最大83695 au,导致了极大的β₀对比,因此碳纳米管成为新型的非线性光学(NLO)开关.新型NLO开关的管径效应表明,较大管径的碳纳米管具有更优的NLO开关性质.除此之外,电子吸收光谱表明这些碳纳米管具有小于300 nm和大于2500 nm的光学工作区,因此碳纳米管可成为一类新的灵敏、快速、可逆的紫外兼红外的NLO开关.     

有机分子二苯乙烯系列衍生物第一超极化率的理论研究

采用耦合-微扰Hartree-Fock方法(CPHF),计算了二苯乙烯系列衍生物的静态第一超极化率.研究发现,具有离域的共轭体系和电子推拉对结构的分子,有利于发生分子内电荷转移,因而具有大的第一超极化率.进一步研究体系中取代基的位置,给体与受体的数量和得失电子的能力,分子的共面性和对称性对分子第一超极化率的影响,结果表明,有机分子拥有更多数量与更强得失电子能力的给体和受体,最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)空间分布的不对称,具有较高的原子共面性和较低的分子中心对称性,都能显著增加 关键词： 二苯乙烯 非线性光学 第一超极化率 空间效应     

氢键分子系统的非线性激发和质子的传导特性

我们首先介绍了氢键系统的特性和质子在此系统中的运动特点及国际上对此问题研究的进展和存在的问题。接着较全面地描述我们提出的新理论的物理学基础、模型的特征和所形成的两类缺陷和质子孤子的特性。这个模型的最大特点是存在两类不同性质的非线性相互作用 ,它们之间的竞争和平衡导致了两类不同的缺陷和相应孤子的出现 ,这两类缺陷的协同和交替运动使质子在氢键系统中从一处传递到另一处。因此 ,此模型能完整地解释质子在氢键系统中的传递 ,在此基础上我们研究了重离子作非简谐振动和系统中存在的杂质及氢离子的迁移所产生的偶极矩等效应对质子孤子的影响以及在外场存在时 ,质子运动的特点 ,求出了质子在电场作用下的迁移率和传导率、大约分别为 (6 5 - 6 .9)× 1 0 - 6(m2 /v .s)和(7.6 - 8.1 )× 1 0 - 3/(Ωm) ,它刚好处在半导体范围内 ,与实验结果基本吻合。并且我们研究了质子传递的量子力学特性和质子孤子存在的临界温度     

边界对石墨烯量子点非线性光学性质的影响

石墨烯作为一种新型非线性光学材料,在光子学领域具有重要的应用前景,引起研究人员的极大兴趣.本文运用量子化学计算方法研究了边界引入碳碳双键(C=C)和掺杂环硼氮烷(B3N3)环对石墨烯量子点非线性光学性质和紫外-可见吸收光谱的影响.研究发现,扶手椅边界上引入C=C双键后,六角形石墨烯量子点分子结构对称性降低,电荷分布对称...     

氢键分子系统的非线性激发和质子的传导特性

我们首先介绍了氢键系统的特性和质子在此系统中的运动特点及国际上对此问题研究的进展和存在的问题。接着较全面地描述我们提出的新理论的物理学基础、模型的特征和所形成的两类缺陷和质子孤子的特性。这个模型的最大特点是存在两类不同性质的非线性相互作用 ,它们之间的竞争和平衡导致了两类不同的缺陷和相应孤子的出现 ,这两类缺陷的协同和交替运动使质子在氢键系统中从一处传递到另一处。因此 ,此模型能完整地解释质子在氢键系统中的传递 ,在此基础上我们研究了重离子作非简谐振动和系统中存在的杂质及氢离子的迁移所产生的偶极矩等效应对质子孤子的影响以及在外场存在时 ,质子运动的特点 ,求出了质子在电场作用下的迁移率和传导率、大约分别为 (6 5 - 6 .9)× 1 0 - 6(m2 /v .s)和(7.6 - 8.1 )× 1 0 - 3/(Ωm) ,它刚好处在半导体范围内 ,与实验结果基本吻合。并且我们研究了质子传递的量子力学特性和质子孤子存在的临界温度     

Solvent effects on structure and optical properties of a D- π-A azobenzene dye

Time-dependent hybrid density functional theory in combination with Onsager reaction field model and super-molecular model has been applied to study solvent effects on the geometrical and electronic structures, as well as one/two-photon absorption properties, of 4-（N-（2-hydroxyethyl）-N-methyl）-amino-4＇-nitroazobenzene. It is found that the short-range interaction has a large effect on the electronic structure of the solute molecule, namely, large red-shift of the maximum one-photon absorption is induced by hydrogen bonding. The solute molecule has a large two-photon absorption cross section, which is enhanced by the solvent effect. The computational results are in good agreement with measurements.[第一段]     

一种新型双共轭链分子非线性光学性质的理论研究

对实验室合成的双共轭链分子1,4-二(4-二乙胺基苯乙烯基)-2-［4-(N-甲基-N-羟乙基)氨基-4′-硝基偶氮苯］-5-己烷氧基苯(BSBAB)及合成它的单共轭链分子的单光子和双光子吸收特性在从头计算的基础上利用密度泛函理论进行了研究.分子BSBAB的优化结构显示，组成该分子的横链和纵链除了保持各自的共轭面外，几近相互垂直.因此，分子BSBAB较好地继承了两个单共轭链分子的光学特性.计算结果表明，在低能量范围内，分子BSBAB具有三个双光子吸收峰，分别来自于两个单共轭链分子以及两者的耦合作用.从理论上证明了双共轭链分子BSBAB是一种具有宽带强双光子吸收的分子材料.理论结果和实验结果符合得较好.在HF水平上的响应函数方法进一步证实了有限态求和方法计算结果的可靠性.还给出了电荷转移态的电荷迁移过程. 关键词： 双光子吸收 双共轭链有机分子 非线性光学     

Linear and nonlinear optical properties of semiconductor particles

Abstract

The field of nonlinear optics is briefly introduced, followed by a review of quantum size effects in small semiconductor particles, with special reference to the linear and nonlinear optical properties. Experimental methods, especially the “laser induced grating” technique are described. Semiconductor (CdS _x Se_1?x ) doped glasses are examined, both the commercially available niters and a specially made experimental CdSe doped glass. Both linear and nonlinear optical properties are discussed. Colloidal and polymers systems are also briefly discussed.     

Vibrational spectral studies on charge transfer and ionic hydrogen‐bonding interactions of nonlinear optical material L‐arginine nitrate hemihydrate

The near infrared Fourier‐transform (NIR FT)‐Raman and Fourier‐transform infrared (FT‐IR) spectroscopies supported by HF/6‐31G(d) computations have been employed to derive equilibrium geometry, vibrational wavenumbers and the first hyperpolarizability of the nonlinear optical (NLO) material, L ‐arginine nitrate (LAN) hemihydrate. The reasonable NLO efficiency, predicted for the first time in this novel compound, has been confirmed by Kurtz–Perry powder second harmonic generation (SHG) experiments. The changes in the atomic charge distribution among different groups due to the presence of strong electronegative atoms and the shrinking of N O bonds of nitrate anion and C N bonds of guanidyl group have been analyzed. The splitting of the carboxylate stretching modes, blue shifting of methine vibrations and the electronic effects such as backdonation and induction on the methylene hydrogen atoms have also been examined in detail. The intense low wavenumber H‐bond Raman vibrations due to electron–phonon coupling and nonbonded interactions in making the LAN molecule NLO active have been discussed based on the vibrational spectral features. The natural bond orbital (NBO) analysis and HF computations confirm the occurrence of strong intra‐ and intermolecular N H·O and O H·O ionic hydrogen bonding between charged species providing the noncentrosymmetric structure in the LAN crystal. Copyright © 2008 John Wiley & Sons, Ltd.     

Linear and nonlinear optical studies on 3,6-bis (2 pyridyl) pyridazine

3,6-Bis (2 pyridyl) pyridazine has been synthesized and characterized by NMR, XRD and elemental analyses. The vibrational studies were carried out by using FTIR and Raman spectroscopy and the modes of vibrations were analysed and compared with the theoretically calculated values. The nonlinear optical property of the title compound was examined by Kurtz–Perry method and Hyper Raleigh scattering with the fundamental wavelength of 1064 nm. This compound possesses less SHG efficiency but large first hyperpolarizability.     

Two-photon absorption properties of aggregation systems on the basis of (E)-4-(2-nitrovinyl) benzenamine molecules

Aggregation effect caused by the intermolecular hydrogen-bonding interactions on two-photon absorption properties of (E)-4-(2-nitrovinyl) benzenamine molecules is studied at a hybrid density functional level. The geometry optimization studies indicate that there exist two probable conformations for the dimers and three for the trimers. A strong red-shift of the charge-transfer states is shown. The two-photon absorption cross sections of the molecule for certain conformations are greatly enhanced by the aggregation effect, from which a ratio of 1.0:2.6:3.6 is found for the molecule and its dimer and trimer with nearly planar structures. Namely, a 30 or 20 percent increase of the two-photon absorption cross section is observed.     

Origin of significant solvent effects on 1J(CC) spin–spin coupling in some acetylenes: hydrogen bonding and solvent polarity

It is demonstrated that some acetylenes, those of the R? C?CH structure, display anomalously high sensitivity to solvent effects of their ¹J(C?C) coupling while R? C?CR acetylenes fail to show that. The solvent‐induced variation in the latter coupling does not exceed 3 Hz; this seems to be the upper limit of variation of any J(CC) and J(CH) coupling in the molecular system studied which included: acetylene (in 13 solvents), phenylacetylene (in 12 solvents), 1‐phenylpropyne, and 2‐hexyne (two solvents each), and the only exceptions are ¹J(C?C) in acetylene, which is shown to vary within about 13 Hz, and that in phenylacetylene where the range amounts to about 8 Hz. These apparent anomalies are explained in the present study in terms of two effects of prime importance, solvent polarity and the solute‐to‐solvent hydrogen bonds where the CH moiety in R? C?CH acetylenes acts as a donor of hydrogen bonds to acceptor sites in the solvent concerned. Copyright © 2009 John Wiley & Sons, Ltd.     

3-溴-4-丁氧基-4'-硝基偶氮苯三阶非线性光学性能的研究

采用Z扫描技术对一种新的偶氮苯类化合物的三阶非线性光学系数进行了测量.实验结果的分析表明,该化合物具有较大的三阶非线性极化率;其三阶非线性主要来源于强的π电子离域性.