荧光激发光谱的突变行为研究

在研究荧光物质的荧光光谱时 ,人们利用激发光谱探讨荧光发射过程中的能量传递与荧光物质分子结构之间的关系。一般认为 ,激发光谱和吸收光谱有着对应的关系 ,甚至是吸收光谱的复制。但是 ,例外却是很多。综合考虑了在传统的测量条件下影响激发光谱的各种因素 ,建立了溶液中荧光物质激发光谱的数学模型 ,并结合突变论的思想对模型加以数学分析。结果表明 ,当样品浓度低于某一浓度上限时 ,样品的激发光谱与吸收光谱具有相同的拓扑结构。但是随着样品浓度的升高 ,激发光谱谱带的拓扑结构会发生一系列的突变的现象。最终导致荧光样品的激发光谱与吸收光谱之间存在很大差异。通过对萘的正己烷溶液荧光激发光谱和吸收光谱进行比较研究 ,从实验上证实了上述理论分析结果的正确性。在传统的测量条件下 ,只有当样品的浓度处于某一极限浓度以下时 ,样品的激发光谱与吸收光谱之间是拓扑等价的。超过这一浓度 ,这种等价关系不再成立。     

盐酸丁卡因与赤藓红的荧光猝灭反应及其分析应用

在pH 4.0的弱酸性介质中,盐酸丁卡因(TA·HCl)与赤藓红(ET)形成1∶1的离子缔合物,导致赤藓红溶液荧光猝灭。当分别于最大激发/最大发射(λ_ex/λem)525 nm/556 nm进行测量时,荧光猝灭值(ΔF)与TA·HCl浓度在0.28～4.8 μg·mL-1范围呈良好的线性关系。该方法灵敏度高,检出限为0.083 μg·mL-1。考察了共存物质的影响,表明方法有良好的选择性。据此发展了一种高灵敏、简便快速测定微量TA·HCl的新荧光分光光度法。该法用于人血清及尿样中盐酸丁卡因的含量测定,结果满意。文章还研究了反应体系的荧光特性,并结合量子化学AM1计算对荧光猝灭机理进行了讨论。     

基于四阶导数的浮游植物叶绿素荧光激发光谱特征研究

测量了分属硅藻和甲藻两个门类的六种我国东海常见赤潮藻的叶绿素荧光激发光谱,以Matlab为操作平台,采用自编的光谱求导程序,对荧光激发光谱进行四阶导数处理。结果表明,四阶导数法能有效去除光谱中的细小杂峰,并将重叠的色素荧光峰分离,实现主要色素的定性定量分析。四阶导数光谱在350～550 nm波长范围内出现的6个极大值主要代表了活体藻液中的非色素荧光物质、叶绿素和类胡萝卜素的荧光峰。通过原始叶绿素荧光激发光谱和四阶导数光谱的对比分析,表明四阶导数光谱法能够凸显硅藻和甲藻之间的光谱差异,增强光谱识别硅藻和甲藻的能力,同时也提高了光谱的稳定性和重现性。     

铝的激发光谱的测量

用１２０ｋｅＶ的Ａｌ＋离子与１０μｇ／ｃｍ２的碳箔相互作用，研究ＡｌⅠ、ＡｌⅡ和ＡｌⅢ的激发光谱，其结果与其它实验进行了比较。     

电子俘获材料Eu,Sm∶CaS荧光特性的研究

研究了电子俘获材料Eu ,Sm∶CaS在室温下的荧光激发谱和荧光辐射谱。荧光激发谱由四个激发带构成 ,是由Eu2 + 的 4f7→ 4f55d跃迁和基质吸收所产生的。可见光激发下的荧光辐射谱是由一个极强的宽带和两个极弱的窄带构成 ,紫外光激发下的荧光辐射谱中不仅出现了以上三个辐射带 ,还出现了七个较强的窄带。这些荧光辐射带分别是由Eu2 + 的 4f65d → 4f7、Sm3 + 的 f→ f、Eu3 + 的 f→ f跃迁所产生的。研究还发现 ,当激剂浓度一定时 ,Eu2 + 的辐射带明显比Sm3 + 的辐射带强。     

血手印的荧光显现

本文在比较使用联苯胺及其衍生物显现血手印的同时，提出了采用荧光显现试剂显现血手印的新方法，文章在简述血红蛋白的组成和性质，通过强氧化剂破坏血红素、沉淀珠蛋白、采用激活血痕、蛋白染色的方法，使血手印清晰显出，并先后开发出用于潜血手印显现的十五种荧光试剂。文章系统论述了血手印荧光显现的原理，讨论了影响血手印荧光显现的各种因素，说明了活化血痕、蛋白染色显微血手印方法、主要特点和显现效果。     

电子俘获材料Eu,Sm：CaS荧光特性的研究

研究了电子俘获材料Eu,Sm:CaS在室温下的荧光激光发谱和荧光辐射谱,荧光激发谱由四个激发带构成,是由Eu^2 的4f^7→4f^55d跃迁和基质吸收所产生的,可见光激光发下的荧光辐射谱是由一个极强的宽带和两个极弱的窄带构成,紫外光激光发下的荧光辐射谱中不仅出现了以上三个辐射带,还出现了七个较强的窄带,这些荧光辐射带分别是由Eu2 的4f^65d→4f^7,Sm^3 的f→f,Eu^3 的f→f跃迁所产生的。研究还发现,当激剂浓度一定时,Eu^2 的辐射带明显比Sm^3 的辐射带强。     

用稀土铕离子的激发光谱测量温度

从理论上探讨了利用稀土离子的激发光谱来测量温度的可能性，并从实验上给予了验证。以ＥｕＣｌ３·６Ｈ２Ｏ粉末作为样品，选择Ｅｕ３＋离子７Ｆ１→５Ｄ０的磁偶极跃迁，由其激发光谱测量了样品的温度。在低于２９０Ｋ时，测量误差小于０．６％。用现有的实验系统和样品，可以准确地测量４０Ｋ至３３０Ｋ的温度。文中对进一步提高测量精度和扩大可测温度范围的途径作了讨论。     

NiI的中性激发光谱和能级寿命的测定

文中描述了利用束箔方法研究能量为１１０ｋｅＶ的Ｎｉ＋离子与厚度为８．５μｇ／ｃｍ２的碳箔相互作用的激发光谱和能级寿命，以及实验测量结果的分析。     

Nd∶YAG中电声耦合非Markovian过程的激发光谱

用Brown振子模型研究YAG基质材料中Nd3+4f电子跃迁的电子声子相互作用过程,详尽推导电子声子耦合的表达式,计算了电声耦合常数不同时的激发光谱,结果表明,电声耦合作用使电子跃迁的吸收峰两边产生声子吸收峰,电声耦合作用较强时,可以产生多级声子吸收峰.通过模拟实验激发光谱,得到样品的电声耦合常数和声子频率等参数,和半导体比较,样品的电声耦合常数较小,说明4f电子声子的耦合属弱相互作用.用这些参数计算时间分辨的荧光相干光谱,其结果与实验结果一致.     

Fluorescence and fluorescence excitation spectra of jet-cooled carbazole

The fluorescence excitation spectra of jet-cooled carbazole molecules at vibrational temperatures of 55 and 80 K and the fluorescence spectrum of these molecules excited by radiation at the frequency of a pure electronic transition are measured. As the vibrational temperature increases, the excitation spectra exhibit a series of lines of the same symmetry, which are caused by the interaction of the active vibration with a subensemble of optically inactive vibrations. The final symmetry of the totally and nontotally symmetric vibrations is determined from the shape of the rotational contours of the lines of vibronic transitions. The values of a decrease in the frequency of the nontotally symmetric vibrations in the first excited electronic state S ₁ due to their interaction with the electronic state S ₂ are calculated to be up to 100 cm^?1. The frequencies of the pure electronic transitions in the absorption and fluorescence spectra coincide with each other and are equal to 30809 cm^?1, the frequencies of vibrations in the ground state S ₀ exceeding the frequencies of the corresponding vibrations in the excited state S ₁. The degree of polarization of the integral fluorescence is determined for a series of vibronic transitions of the a ₁ and b ₂ final symmetry that are observed in the fluorescence excitation spectra, and the contribution of the intensity with the borrowed polarization θ_⊥ to the integral fluorescence is calculated. It is found that the intensity θ_⊥ is higher for the transitions of the b ₂ symmetry and can reach ≈50%.     

Quantum-resolved fluorescence excitation spectra of SnO free radical

TheA ¹ –X ^{1 +} system of SnO is studied by laser- induced fluorescence excitation spectroscopy using isotopically enriched tin Sn¹¹⁶. The rotational structure analysis has been carried out for 6-0, 5-0, 2-0 bands. All these spectra were well resolved only with few perturbed lines in 2-0 band. Rotational constantsB ₂,B ₅,B ₆ and henceB _e , _{e e} have been obtained for the Sn¹¹⁶O molecule. An extension of perturbation study on 4-0 band has been made showing the maximum perturbation occurs at different J values for different isotopes.     

The fluorescence spectra of pharmaceutical compounds under two-photon excitation

Spectra of two-photon-excited fluorescence in pharmaceutical crystalline compounds were obtained and studied as functions of the pump power and delay time. Stimulated fluorescence was observed in polycrystalline Novocaine under high-power pumping. The spectra of two-photon-excited fluorescence in pharmaceutical compounds are localized within the wavelength range of 270–480 nm. The most intense fluorescence was observed in the Novocaine polycrystals. The therapeutic effect of diphenylhydramine and sulfanilamide is attributed to the fact that the energy of optical quanta of the fluorescence emission in these substances is higher than the energy of excited π-electrons in tryptophan and nucleotides. The data obtained for the spectra of the pharmaceutical substances studied can be used to solve analytical problems related to identification of the composition and properties of composite pharmaceutical substances.     

Fermi-type resonance in quasi-linear fluorescence excitation spectra of triazatetrabenzoporphine

The effect of deuteration of the central NH groups on the quasi-linear fluorescence and fluorescence excitation (with selective monitoring) spectra for triazatetrabenzoporphine, a close analog of phthalocyanine, has been investigated at 77K in n-nonane. Vibrational analysis of the spectra was carried out. The normal mode frequencies were determined for the electronic states S₀ (from fluorescence spectra) and S₁ (for fluorescence excitation spectra). It has been established that N-deuteration lowers the frequency of a vibration involving inplane NH bending down to ∼990 cm⁻¹ and leads to resonant vibrational-electronic (vibronic) interaction of Fermi-type resonance between the zero level of the S₂ state and the vibronic level of the S₁ state upon excitation of this mode. Thereby the possibility of the “vibronic analog of Fermi resonance” (a term coined by G. Herzberg) occurring in a simple (two-component) variant of phthalocyanine-type molecules has been shown. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 796–803, November–December, 2008.     

Vibronic fluorescence and fluorescence excitation spectra of diphenyl oxazolyl benzene and its oxadiazol analogue

The fine-structure fluorescence and fluorescence excitation spectra of conjugated chain compounds—1,4-di(5-phenyl-2-oxazolyl) benzene and its oxadiazol analogue—are obtained at 4.2 K in an n-octane matrix using the Shpolskii method. The spectra are modeled by representing the band of each of the vibronic transitions as the sum of a zero-phonon line and a phonon wing with certain parameters (half-widths, Debye-Waller factors). The spectra calculated in this fashion coincide with the experimental spectra. This makes it possible to determine the relative intensities of vibronic transitions and refine the frequencies of the normal vibrations in the S ₀ and S*₁ states. The parameters of the Franck-Condon and Herzberg-Teller interactions in the molecules considered are determined. The influence of the replacement of one of the CH groups in the heterocycles with a N atom on the parameters determining the formation of vibronic spectra is considered.     

Effect of excitation intensity on fluorescence spectra in ZnO nanostructures and its origin

ZnO nanostructures with three kinds of morphologies, namely, tetrapod-, rod-, and sheet-like shape, are synthesized by chemical vapor deposition, conventional solution-phase, and hydrothermal methods, respectively. The fluorescence measurements display that the spectra of these nanostructures exhibit similar unexpected change laws with the altering excitation intensity. It is observed that when the excitation intensity increases, for the green emission band, the peak position shows a small blue-shift, the width turns broader, and the intensity grows first stronger and then weaker; for the UV emission band, the peak position exhibits a significant red-shift, and the width and intensity have the similar behaviors with those of the green band. Additionally, the relative intensity of green emission to UV emission decreases gradually. It is clarified that the origin of this abnormal phenomenon is ascribed to the local laser heating effect and the high sensitivity of nanostructures to this heating effect. Supported by the National Basic Research Program of China (Grant No. 2005CB623603)