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激发态质子转移是光物理学、光化学和光生物过程中最基本的化学反应之一。激发态分子内质子转移(excited-state intramolecular proton transfer, ESIPT)通常是指有机分子受到激发,到达激发态后,质子在激发态势能面上从质子供体基团转移到质子受体基团并形成含有分子内氢键多元环的过程, 一般发生在亚皮秒量级。质子转移可应用于有机发光二极管、荧光探针等领域。茜素,即1,2-二羟基蒽醌,可从茜草根部提取,具有与醌类衍生物相似的结构,常用于染料、染色剂和药物等。近年来,发现茜素分子具有质子转移特性,可用来制备新型“绿色”染料敏化电池。利用稳态吸收、稳态荧光和飞秒瞬态吸收光谱技术以及第一性原理理论计算对溶于乙醇溶液的茜素分子的质子转移过程进行了研究和分析。稳态吸收和稳态荧光研究结果表明: 在基态时,茜素分子的正常构型9,10-酮处于稳定状态,容易发生跃迁;在激发态时,茜素分子的互变异构体构型1,10-酮处于稳定状态,容易产生荧光发射。飞秒瞬态吸收光谱测量使用的激光的激发波长为370 nm。测得的瞬态吸收光谱在430 nm附近存在茜素的基态漂白信号。通过使用全局拟合方法对瞬态吸收光谱进行分析研究发现:茜素正常构型9,10-酮的激发态分子内质子转移时间为110.5 fs,茜素互变异构体构型1,10-酮分子内振动弛豫时间为30.7 ps,茜素互变异构体构型1,10-酮荧光寿命为131.7 ps。通过使用单波长动力学拟合的方法对瞬态吸收光谱进行分析发现:发生质子转移的时间尺度与运用全局拟合方法得出的结果基本一致;茜素分子的正常构型9,10-酮分子在110.5 fs的时间尺度内处于快速减少的趋势,而茜素分子的互变异构体构型1,10-酮分子在这一时间尺度内处于快速上升的趋势。当延迟时间增大时,茜素分子的互变异构体构型1,10-酮分子又呈现缓慢衰减的趋势。 相似文献
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L. Cerdán A. Costela I. García-Moreno O. García R. Sastre 《Applied physics. B, Lasers and optics》2009,97(1):73-83
The characteristics of amplified spontaneous emission (ASE) from asymmetric planar waveguides and quasi-waveguides consisting
of thin films of poly(methyl methacrylate) incorporating lasing dye pyrromethene 597 deposited onto quartz and glass substrates,
respectively, are investigated. The variable stripe length and moving constant stripe methods, together with appropriate theoretical
expressions which take into account gain saturation and a simple model based on a four-level laser, allow for obtaining the
net gain coefficients as a function of pump intensity, losses, pump thresholds for the onset of ASE, effective stimulated
emission cross sections, pump saturation intensities, and saturation lengths. Net gain coefficients of up to 84±3 cm−1 at a pump intensity of 404 kW/cm2 (28 μJ/pulse) for quasi-waveguides and up to 59±6 cm−1 at a pump intensity of 360 kW/cm2 (25 μJ/pulse) for waveguides were obtained, with pump thresholds of 15.7 kW/cm2 (1.1 μJ/pulse) and 6.3 kW/cm2 (0.43 μJ/pulse), respectively. When waveguides 8 μm thick were irradiated with pulses of 200 kW/cm2 at 10 Hz repetition rate, the ASE remained at 79% of its initial value after 1000 pump pulses in the same position of the
sample. In quasi-waveguides 10 μm thick, the emission remained at 82% of the initial value under the same conditions. 相似文献
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A. Sagisaka H. Daido S. Nashima S. Orimo K. Ogura M. Mori A. Yogo J. Ma I. Daito A.S. Pirozhkov S.V. Bulanov T.Zh. Esirkepov K. Shimizu M. Hosoda 《Applied physics. B, Lasers and optics》2008,90(3-4):373-377
We have observed simultaneously both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction
with a 5-μm thick titanium target. In order to control the proton acceleration and THz radiation, we have changed the duration
of the amplified spontaneous emission (ASE) preceding the main pulse generated by the high-intensity Ti:sapphire laser. A
fast proton beam with the maximal energy of ∼ 490 keV has been realized by reducing the duration of the ASE. Simultaneously,
an intense emission of THz radiation is observed for various ASE durations. We propose the antenna mechanism for the THz radiation,
according to which the fast electrons moving along the target surface emit the low-frequency electromagnetic wave.
PACS 52.25.Os; 52.38.Kd; 52.50.Jm 相似文献
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2-(2''''-羟基苯基)间氮杂氧茚放大的自发辐射效应的实验和理论研究 总被引:1,自引:1,他引:0
报道了在氮分子激光泵浦下,激发态分子内质子转移分子2-(2'-羟基苯基)间氮杂氧茚(HBO)环乙烷溶液放大的自发辐射(ASE)实验和理论研究。在环己烷溶液中,HBO的增益系数α(510um)约为1.2cm-1。在建立了HBO激发态分子内质子转移(ESIPT)的放大的自发辐射动态模型基础上,通过数值模拟得到了HBO的增益光谱和放大的自发辐射光谱,计算结果与实验很好相符,证实了HBO的酮式异构体的基态寿命更接近于260ns而非亚纳秒级。 相似文献
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通过对RhB/PMMA和Rh6G/PMMA染料薄膜的荧光光谱和放大自发辐射(ASE)光谱的实验测量和理论分析,研究了准波导结构染料薄膜的荧光光谱和ASE光谱特性。实验上采用连续激光和脉冲激光照射,分别测量准波导结构RhB/PMMA和Rh6G/PMMA染料薄膜的荧光光谱和ASE光谱,发现荧光峰和ASE峰随着染料掺杂浓度和薄膜厚度的增加产生红移;理论上考虑准波导结构下薄膜中染料的自吸收效应,类比激光器谐振腔模型,分析低阶导模传输的增益特性,获得了荧光光谱与ASE光谱中荧光峰和ASE峰对应波长与染料掺杂浓度的关系,数值计算与实验测量相吻合。结果表明,准波导结构下薄膜中染料自吸收效应导致荧光峰及ASE峰发生红移,改变染料掺杂浓度,可以在较大调谐范围实现ASE。 相似文献
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Influence of the solvent environments, pumping pulse energies and concentrations on the spectral properties of 1,2,3,8-tetrahydro-1,2,3,3,5-pentamethyl-7H-pyrrolo[3,2-g]quinolin-7-one (LD-423) have been investigated. The photophysical characteristics such as absorption, fluorescence spectra, Stokes’ shift, fluorescence quantum yield, absorption, emission cross sections, extinction coefficient and amplified spontaneous emission (ASE) were measured. Here, LD-423 showed two ASE in a certain organic solution under pulsed laser excitation (Nd: YAG λex?=?355 nm). One of these peaks corresponds to the fluorescence, while the other peak is an anomalous peak which does not have a corresponding fluorescence peak. This abnormal ASE peak can be ascribed to the fact that the excited molecules are connected in the excited state and the solvent acts as a link between them. 相似文献
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We previously applied the electrochromic modulation of excited-state intramolecular proton-transfer (ESIPT) reaction for the
design of novel 3-hydroxyflavone (3-HF) derivatives as fluorescent probes for measuring the dipole potential, ΨD, in lipid bilayers (Klymchenko et al., Proc. Natl. Acad. Sci. USA, 2003, 100, 11219). In the present work, this method was revisited to take into account the influence of the bilayer hydration on the
emission ratiometric response of 3-HF probes. For this reason, it was necessary to deconvolute the whole fluorescence spectra
into three bands corresponding to the non H-bonded forms, normal N* and tautomer T* forms, both participating to the ESIPT reaction, and to the H-bonded H–N* form, excluded from this reaction. This allowed us to determine the pure N*/T* intensity ratio, without any contribution from the H–N* form emission depending essentially on the bilayer hydration. This new approach allowed us to confirm the correlation we
obtained between the response of 3-HF probes on dipole potential modifications and the corresponding response of the reference
fluorescent probe di-8-ANEPPS, thus further confirming the potency of 3-HF probes as excellent emission ratiometric probes
to measure dipole potential in lipid membranes. 相似文献
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自发辐射(ASE)是掺铒光纤放大器(EDFA)的重要噪声源,对于由EDFA构成的光纤激光器有重要影响。理论与实践证明,它与抽运方式紧密相关,所以研究脉冲抽运时掺铒光纤(EDF)的自发辐射有重要的学术价值。同时,脉冲抽运对于EDFA锁模激光器的研究也有一定意义。从理论和实验两方面研究了小信号脉冲抽运时,抽运脉冲宽度和幅度对于EDF的自发辐射特性的影响,得到了小信号抽运时输出ASE噪声平均值的近似解析解。研究发现,小信号脉冲抽运时输出信号的幅度与抽运脉冲的宽度成正比。这个新现象可用于脉冲宽度的全光检测。 相似文献
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A rate-equation model for describing the travelling-wave amplified spontaneous emission pulses (TWASE) in a transversally excited travelling wave arrangement is given. 6.35 ps long ASE pulses have been obtained by 12 ps long pump pulses. The effect of pump intensity, pump-pulse duration, molecular parameters of the dyes and pump-sweep velocity on the ASE pulses is studied. 相似文献
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Eric R. Tkaczyk Alan H. Tkaczyk Koit Mauring Jing Yong Ye James R. Baker Jr. Theodore B. Norris 《Journal of fluorescence》2009,19(3):517-532
We present a comprehensive study of the selective excitation of two-photon fluorescence from various pairs of dyes and dyes in different conjugation states with tailored pulse shapes found with a genetic algorithm (GA). We investigate a number of biologically important dyes, and include dyes conjugated to trastuzumab (Herceptin®) and to a poly(amidoamine) dendrimer. We consider in detail the ability of tailored pulse shaping to discriminate dyes with significant spectral overlap. Our procedure for adaptive pulse shaping includes power-law and chirp-scaling checks to prevent trivial convergences. The GA uses a multiplicative fitness parameter in a graded search method that converges on pulse shapes that not only differentiate two-photon processes, but do so in a high signal regime. We consider the results in terms of not only the absolute maximum ratio of discrimination achieved, but also present the evolutionary course of the GA and compare the improvement to a quantitative measure of the noise level. We also implement a time-domain acousto-optic measurement of two-photon excitation cross-section spectra. The results show that the ability to discriminate dyes is determined almost entirely by their differences in two-photon excitation cross section. 相似文献
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Fluorescence of Styryl Dyes-DNA Complexes Induced by Single- and Two-Photon Excitation 总被引:1,自引:1,他引:0
Tokar VP Losytskyy MY Kovalska VB Kryvorotenko DV Balanda AO Prokopets VM Galak MP Dmytruk IM Yashchuk VM Yarmoluk SM 《Journal of fluorescence》2006,16(6):783-791
The series of novel monomer and homodimer styryl dyes based on (p-dimethylaminostyryl) benzothiazolium residues were synthesized and studied as possible fluorescent probes for nucleic acids
detection. Spectral-luminescent and spectral-photometric properties of obtained dyes in the unbound state and in DNA presence
were studied. Fluorescence emission induced by two-photon excitation of dye-DNA complexes in aqueous buffer solution was registered.
Two-photon absorption cross section values of the studied dyes in DNA presence were evaluated. 相似文献
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C. E. Chryssou 《Fiber and Integrated Optics》2001,20(6):581-590
A 16-channel, 2.5 Gb/s, wavelength-division multiplexing system is analyzed with its channels allocated in the 1.52-1.56 μm wavelength region in order to increase the usable amplifier bandwidth to ≈45 nm. To avoid amplified spontaneous emission (ASE) noise and the nonuniform signal gain in the wavelength region, an amplifier module consisting of an Er 3+ -doped tellurite waveguide amplifier, an ASE filter, and two concatenated long-period grating filters are proposed. A tellurite-based amplifier was chosen as the amplifying element because of its broad emission bandwidth (~80 nm), its high emission cross section (6.44 ×10 -25 m 2 ), and its high rare-earth ion solubility. The amplifier model is based on propagation and populationrate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining finite elements and a Runge-Kutta algorithm. The analysis predicts that using the proposed amplifier module, the channels may be transmitted to a maximum distance of 1800 km, finding applications in large optical networks where either many wavelengths are required or channel spacing must be large. 相似文献
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A theoretical amplification gain equation is derived in the case of an abscissa-dependent steady-state concentration of excited molecules, including triplet-triplet absorption effect. The non-exponential gain which results gives a method for measuring directly the emission cross section from the thermalized emitting state without involving the fluorescent quantum yield. Comparison with experimental results measured in a rhodamine 6G amplifier fully justifies the theoretical equation and confirms the absolute value of the emission cross section for this molecule. With the amplifier used, a maximum power amplification value of 230 was observed for a 33 W/cm2 input pulse. At higher energy levels, outputs of up to 3.7 MW/cm2 (1 joule) in 5 Å and 2 mrad were obtained. 相似文献
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A. Ghoshal P. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):327-335
e+ + H(ns) ↦e+ + H(n′s) transitions for arbitrary n and
n′ have been studied using the distorted-wave formalism in the
momentum space [Ghoshal and Mandal, Phys. Rev. A 72, 032714 (2005)]. The distorted-wave
scattering amplitudes have been written in a simple closed analytical form. A detailed
study has been made on differential and total cross sections in the energy range 20–300 eV.
Resonance-like behaviour of the
differential cross section has been observed in the the region of lower scattering angles
for high Rydberg transitions. To the best of our knowledge the distorted-wave results for
differential and total cross sections for such arbitrary transitions are reported for the
first time in the literature. 相似文献
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运用掺镱双包层光纤放大器的理论模型,分析了连续和脉冲光放大时放大自发辐射(ASE)的计算方法。采用Runge-Kutta方法求解了考虑ASE稳态时掺镱双包层光纤放大器的放大特性,采用有限差分法求解了矩形、高斯和超高斯脉冲的放大特性。结果表明:用3 m长的双包层光纤、10 W的泵浦功率可以将脉宽3 ns、峰值功率为1 W的脉冲信号光峰值功率放大到15 kW左右;在饱和增益情况下,脉冲的波形变尖,宽度变窄;采用短的大模场双包层光纤和后向泵浦方式可以有效地降低ASE,并避免有害非线性效应。 相似文献
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The suppression of amplified spontaneous emission (ASE) that arises during the femtosecond chirped-pulse amplification is presented. On the basis of the distinct differences in the spatial, temporal and spectral region between ASE and the amplified laser signal, the noise arising from ASE was effectively filtered out. The ratio between the amplified femtosecond pulse and the ASE peak power was higher than 107. Pulses as short as 38 fs were amplified to peak power of 1.4 TW. 相似文献
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The amplified spontaneous emission (ASE) spectra of the conjugated polymer [2-methoxy-5-(2′- ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is investigated under different conditions such as thin film and solution, solvent type and concentration. Results indicate that aggregation has a pronounced effect on ASE spectra. In solution form, as concentration was increased and thus the proportion of aggregates, a decrease in the ASE emission bandwidth and a red shift of the ASE peak was observed. For the thin film samples, the ASE spectra show two emission bands which were assigned to the first and second vibronic transition of the polymer chains. 相似文献