溶剂对N-{4-[(反式)-2-(4-硝基苯基)乙烯基]苯基}-N,N-二苯氨基分子双光子吸收特性的影响

在从头计算的基础上,利用两态模型对溶剂对N-{4-[(反式)-2-(4-硝基苯基)乙烯基]苯基}-N,N-二苯氨基分子双光子吸收特性的影响进行了理论研究.计算结果表明,溶剂对该分子的双光子吸收截面影响较大,双光子吸收截面随着溶剂极性的增加而增加.     

三苯胺衍生物分子非线性光学性质的理论研究

在密度泛函理论水平上,利用响应函数方法,研究了1-{(1E)-2-[4-(二苯胺基)苯基]乙烯基}-4-[4-N,N-二甲胺]苯(PVMB)和1-[(1E)-2-(4-(1E)-2-{4-[4-N,N-二甲胺]苯基}乙烯基)苯基]苯胺}苯基)乙烯基]-4-[4-N,N-二甲胺]苯(DPVMB)两分子的双光子吸收特性.计算结果表明,这两个化合物都具有较好的双光子吸收特性,且具有两分支结构的DPVMB分子比具有单支结构的PVMB分子有更强的双光子吸收强度.计算数值结果和实验结果符合地较好.     

双氰基荧光染料的合成、光学性质及其生物成像

设计合成了一种A-π-D-π-A型的双光子荧光染料3,6-双(4-乙烯基苯腈)-9-乙基咔唑,测试了其在二氯甲烷(DCM)、乙酸乙酯(EA)、乙醇(Et OH)、乙腈(ACN)、二甲亚砜(DMSO)和磷酸缓冲盐溶液(PBS)等不同溶剂中的紫外吸收光谱、单光子及双光子荧光光谱。化合物3,6-双(4-乙烯基苯腈)-9-乙基咔唑在紫外吸收光谱中存在两个相似的特征吸收带并呈现出复杂的溶剂化效应,在DMSO中具有最大荧光量子产率(86.02%),其相应的活性吸收截面为12.56 GM。在双光子荧光成像方面,染料分子具有优良的细胞膜通透性并且在双光子荧光显微镜下呈现出明亮的绿色荧光,表现出较好的双光子荧光成像性能。这些数据表明,化合物3,6-双(4-乙烯基苯腈)-9-乙基咔唑可用作一种较为理想的双光子荧光标记染料。     

新型多共轭链有机分子双光子吸收特性的理论研究

在密度泛函理论水平上,利用解析响应函数方法研究了以（4-{2-［4-（2-吡啶-4-乙烯基）-苯基］-乙烯基}-苯基）-胺为基本结构单元的单支、双支和三支共轭链有机分子的单光子和双光子吸收特性.计算结果表明,这三种有机分子都具有较大的线性和非线性吸收强度.在紫外-可见光区域,它们的单光子吸收谱都存在两个峰,这与实验结果符合较好.在近红外区域,多共轭链有机分子呈现出宽达300 nm的宽带双光子吸收,单支、双支和三支分子的最大双光子吸收截面比约为1.0∶2.3∶4.0,其中三支分子具有最大的双光子吸收截面101.73×10^-48 cm⁴·s.从理论上进一步证实,增加分子的共轭链可有效提高分子的双光子吸收特性.同时还给出了电荷转移态的电荷迁移过程. 关键词： 双光子吸收 响应函数方法 多共轭链有机分子     

一种新型偶氮化合物的纳秒光限幅特性研究

研究了反式—4—{[p—(N,N—二羟乙基胺基)偶氮苯]乙烯基}吡啶在N,N—二甲基甲酰胺(DMF)中的光限幅性能。实验结果表明,该偶氮化合物的DMF溶液对波长为532nm,脉冲宽度为8ns的激光脉冲具有很强的光限幅特性。理论分析表明,光限幅效应主要起源于材料的双光子吸收。利用双光子吸收模型拟合光限幅实验数据得到材料的双光子吸收系数β=1.6×10-9cm/W。     

两种三光子吸收染料光限幅性能的实验研究

研究了两种新型D-π-D结构的芴类衍生物4-{7-[4-（二甲基胺）苯基]-9,9-二（2-乙基己基）-9H-芴-2-}-N,N-二甲基苯胺[缩写为B（DMAP）F]和4-{2-[7-（4-氨基苯乙烯基）-9,9-二（2-乙基己基）-9H-芴-2-]乙烯基}苯胺（缩写为BASF）在四氢呋喃（THF）和N,N-二甲基甲酰胺（DMF）中的线性吸收和单光子荧光行为,用脉冲宽度为38ps,重复频率为10Hz的1064nmNd;YAG脉冲激光研究了两种化合物的三光子吸收性质,结果表明：受溶剂效应的影响,两种化合物在极性较大的四氢呋喃溶剂中的最大线性吸收峰和荧光发射峰都有所红移;在极性较大溶剂中三光子吸收截面的数值较大,最高达到10^ -76cm^6S^2数量级。两种新材料还表现出明显的三光子吸收光限幅效应,当入射光强为8GW／cm^2时,B（DMAP）F和BASF的非线性透过率分别达到35％和39％。     

多维树枝状有机分子的双光子吸收特性

利用响应理论方法,研究了新近合成的以二-(苯乙烯基)苯为主干的多分枝有机物的双光子吸收特性.结果表明这些多维有机分子显示了较好的双光子吸收特性,其中A-π-A型的有机分子具有较大的双光子吸收截面,进一步说明了到底是对称型的还是不对称型的有机分子具有大的双光子吸收截面还与分子的π中心有关.     

多维树枝状有机分子的双光子吸收特性

利用响应理论方法，研究了新近合成的以二-(苯乙烯基)苯为主干的多分枝有机物的双光子吸收特性。结果表明这些多维有机分子显示了较好的双光子吸收特性，其中A-π-A型的有机分子具有较大的双光子吸收截面，进一步说明了到底是对称型的还是不对称型的有机分子具有大的双光子吸收截面还与分子的π中心有关。     

咔唑类化合物的光谱特性与三光子激射

测量了一系列新合成的咔唑类化合物的光谱特性。光谱研究结果发现端基团的选择引起双光子吸收截面的巨大变化。用1.3 μm强fs激光激发其中一双光子吸收截面高达617.3 GM的分子溶液,其波长和时间分辨光谱特性表明此分子的高方向性光发射是三光子诱导激射。[1 GM(Gppert-Mayer)=10-50 cm4·s·(photon)-1]。     

4，4′-二甲氨基二苯乙烯双光子吸收理论研究——溶剂效应

对最近实验室合成的分子材料4，4′-二甲氨基二苯乙烯的双光子吸收特性在从头计算的基础上进行了理论研究。理论模型是建立在密度泛函理论的基础上的。利用含时的密度泛函理论来计算分子的非线性光学性质，而溶剂效应则通过自洽响应场方法的极化连续模型来模拟。计算结果表明，三态模型可以很好地给出该分子在低激发态范围内的双光子吸收截面。随着溶剂极性的增加，单光子波长红移，双光子吸收截面增加。双光子吸收截面的大小和实验给出的结果符合得较好。     

Solvent effects on optical properties of a newly synthesized two-photon polymerization initiator： BPYPA

Time-dependent hybrid density functional theory in combination with polarized continuum model is applied to study the solvent effects on the geometrical and electronic structures as well as one- and two-photon absorption processes, of a newly synthesized asymmetrical charge-transfer organic molecule bis-（4-bromo-phenyl）-[4-（2-pyridin-4-yl-vinyl）phenyl]-amine （BPYPA）. There exist two charge-transfer states for the compound in visible region. The two-photon absorption cross section calculated by a three-state model and solvatochromic shift of the charge-transfer states are found to be solvent-dependent, where a nonmonotonic behaviour with respect to the polarity of the solvents is observed. The numerical results show that the organic molecule exhibits a rather large two-photon absorption cross section as compared with the compound 4-trans-[p-（N, N-Di-n-butylamino）-p-stilbenyl vinyl] pyridine （DBASVP） reported previously, and is predicted to be a good two-photon polymerization initiator. The hydrogen-bond effect is analysed. The computational results are in good agreement with the measurements.     

Static and Ultrafast Transient Photophysics of Mono- and Dual-Branched Triarylamines

Mono- and dual-branched molecules, { 4-[2-（4-benzothiazol-2-yl-phenyl）-vinyl]-phenyl}-（4-methoxy-phenyl）-phenyl- amine （BS1） and bis-{4-[2- （4-benzothiazol-2-yl-phenyl）-vinyI]-phenyl}-（4-methoxy-phenyI）-phenyl-amine （BS2）, are investigated with one- and two-photon static spectroscopy, and the femtosecond fluorescence up-conversion technique. The molecules show branch-based fluorescence emission at low quantum yield. U1trafast non-radiative decay on a picosecond time scale is found and is attributed to intramolecular charge-transfer bridged by the central triphenylamine. The two-photon absorption cross-sections of BS1 and BS2 are 19.1 and 19.4 GM, respectively.     

Molecular Geometry Optimization, Two-Photon Absorption and Electrochemistry of New Diphenylethylene Derivatives Linking with Benzophenone Moiety Through Ether Covalent Bond

This paper presents the molecular geometry optimization, two-photon absorption and electrochemistry of new dyes containing benzophenone part, including 4-(p-benzoyl-benzyloxy)yl-4'-nitro-diphenylethylene (C1), 4-[N-methyl-N-(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenylethylene (C2), 4-[N-ethyl-N-(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenylethylene (C3), and 4-N, N-bis[(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenyl ethylene (C4). The molecular structural parameters show that the coplanarity of diphenylethylene moiety is diminished in the excited state for C1, while it is enhanced for C2, C3 and C4. The electron density distribution of frontier orbital suggests that the derivatives exhibit (π, π) transition with internal charge transfer character, and the extent of charge transfer of C2, C3 and C4 is larger than that of C1. The derivatives display remarkable two-photon absorption (TPA) induced up-converted emission under 800 nm Ti: Sapphire femtosecond laser excitation. The maximal TPA emission wavelength of C2, C3 and C4 is red-shifted with respect to that of C1. TPA cross sections of C2, C3 and C4 are larger than those of C1. The cyclic voltammograms and the fluorescence lifetimes of the derivatives were determined and discussed.     

Accurate studies of dissociation energies and vibrational energies on alkali metals

This paper studies full vibrational spectra {Ev} and molecular dissociation energies De by using conventional least-squares （LS） fitting and an algebraic method （AM） proposed recently for 10 diatomic electronic states of ^7Li2, Na2, NaK and NaLi molecules based on some known experimental vibrational energies in a subset [Ev^expt] respectively. Studies show that： （1） although both the full AM spectrum {Ev^AM} and the LS spectrum {Ev^LS} can reproduce the known experimental energies in [Ev^expt], the {EAM} is superior to the {Ev^LS} in that the high-lying AM vibrational energies which may not be available experimentally have better or much better accuracy than those LS counterparts in {Ev^LS}, and so is the AM dissociation energy De^AM; （2） the main source of the errors in the data obtained by using the LS fitting is that the fitting which is just a pure mathematical process does not use any physical criteria that must be satisfied by the full vibrational spectrum, while the AM method does. This study suggests that when fitting or solving a physical equation using a set of source data, it is important not only to apply a proper mathematical tool, but also to use correct physical criteria which measure the physical properties of the data, kick out those data having bigger errors, and impose conditional convergence on the numerical process.     

Nonlinear two-photon absorption properties induced by femtosecond laser with the films of two novel anthracene derivatives

Two novel anthracene derivatives containing 4-vinylpyridine (FPEA) and 2-vinylpyridine (TPEA) poly(methyl methacrylate) films are prepared on quartz glass substrates. Their nonlinear absorption properties are investigated by using a 120-fs, 800-nm Ti:sapphire femtosecond pulsed laser operating at a 1-kHz repetition rate. The unique nonlinear absorption properties of these new compounds are observed by utilizing a Z-scan system. These two-photon absorption (TPA) properties are proven by the two-photon fluorescence excited at 800 nm. The FPEA and TPEA films have nonlinear TPA coefficients of 0.164 and 0.148 cm/GW and the TPA cross sections of 3.345 × 10-48 and 3.081 × 10-48 cm4 ·s/photon, respectively. The influence of the chemical structures on the nonlinear TPA properties of the compounds is also discussed. The highly nonlinear TPA activities of the films implied that the new anthracene derivatives are suitable materials with promising applications in super-high-density three-dimensional data storage and nano- or microstructure fabrication.     

Theoretical studies on the one- and two-photon absorption properties of azulenylporphyrins and azulene-fused porphyrins

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d) and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400--600~nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.     

Two-photon absorption in two-dimensional conjugated quadrupolar chromophores

We present ultrafast z-scan measurements of the two-photon absorption (TPA) spectra of a pair of two-dimensionally conjugated quadrupolar donor/acceptor (D/A) chromophores. The all-donor substituted species displays a peak TPA cross section [sigma(2)=520+/-30 GM] that is more than twice that of the D-A species [sigma(2)=240+/-20 GM]. Unlike previous structure-property studies that have evaluated TPA behavior for D/A molecules through the comparison of dipolar and quadrupolar compounds, both molecules investigated herein are quadrupolar, ultimately providing a more consistent evaluation of the effects of donor and/or acceptor substitution on the TPA of conjugated chromophores.     

Two-photon absorption and laser photolysis of trans-stilbene substitutes

The measured the two-photon absorption (TPA) cross sections of ethanol solution of trans-stilbene and its two substitutes excited by nanosecond radiation of the 2nd harmonic of a Nd:YAG laser (532 nm) are presented. To determine the TPA cross section, a method based on measurements of photochemical decomposition of molecules of the examined compounds having low photostability is suggested. The measured value of the TPA cross section of trans-stilbene in ethanol is found to be 25 GM, and the TPA cross sections of the trans-stilbene substitutes are found to be 60 and 70 GM. The TPA cross section of trans-stilbene substitutes obtained in the present paper is compared with the experimental and theoretical data obtained by other authors. The results of investigations demonstrate that the photochemical decomposition method can be successfully used to determine experimentally the two-photon absorption cross section of the compounds unstable under photoexcitation, including photochromatic molecules, biological objects, and radical photoinitiators.