激光诱导时间分辨固体表面荧光光谱系统

采用斜射式激发样品光路结构,设计了应用于测试时间分辨固体表面荧光光谱系统。利用该系统研究了氧化锌薄膜在355 nm激光脉冲激发下的时间分辨固体表面荧光光谱。结果表明,该系统能够实现测量时间分辨固体表面荧光光谱,并由此测量了样品的固体表面荧光寿命。该系统结构简单可靠,灵敏度高,响应速度快。     

激光等离子体受激Raman散射光谱的时间分辨测量

采用光学多道谱仪和光学条纹相机耦合,组成时间分辨的Raman散射光谱测量系统,可实现0.5nm的光谱分辨和好于10ps的时间分辨。采用该测量系统,在神光Ⅱ装置上开展了脉宽1ns、波长351nm的激光与两种不同尺寸柱腔靶相互作用的物理实验,获得了时间分辨的SRS光谱实验结果。研究表明,SRS光谱在时间上相对于入射激光有一定的延迟,腔靶尺寸减小时,延迟时间随之减小。通过长、短波截止波长分析电子密度方法,计算得出了Ⅰ型和Ⅱ型腔靶SRS散射光最短波长光谱发生的密度区分别为0.069nc和0.027nc。     

Low-temperature time-resolved vacuum ultraviolet spectroscopy of self-trapped excitons in KH<Subscript>2</Subscript> PO<Subscript>4</Subscript> crystals

A complex investigation of the dynamics of electronic excitations in potassium dihydrophosphate (KDP) crystals is performed by low-temperature time-resolved vacuum ultraviolet optical luminescence spectroscopy with subnanosecond time resolution and with selective photoexcitation by synchrotron radiation. For KDP crystals, data on the kinetics of the photoluminescence (PL) decay, time-resolved PL spectra (2–6.2 eV), and time-resolved excitation PL spectra (4–24 eV) at 10 K were obtained for the first time. The intrinsic character of the PL of KDP in the vicinity of 5.2 eV, which is caused by the radiative annihilation of self-trapped excitons (STEs), is ascertained; σ and π bands in the luminescence spectra of the STEs, which are due to singlet and triplet radiative transitions, are resolved; and the shift of the σ band with respect to the π band in the spectra of the STEs is explained.     

The role of built-in electric fields in the InGaN/GaN quantum-well emission

By analyzing the evolution of time-resolved photoluminescence spectra, it is detected experimentally for the first time that there is a correlated effect of built-in electric fields and of long-lived localized states on the formation of emission in quantum wells based on nitrides of Group III elements. It is shown that light-emitting diode structures can be classified for commercial applications by studying time-resolved photoluminescence spectra.     

Femtosecond fluorescence upconversion setup with broadband detection in the ultraviolet

We show a femtosecond fluorescence upconversion setup with broadband detection to measure time-resolved emission spectra in the 300-550 nm range, upon excitation between 250 and 300 nm, with a time resolution of 100 fs. We present time-resolved fluorescence emission spectra of 2,5-diphenyloxazole in solution, which demonstrate the capabilities of the setup.     

Time-resolved photoluminescence spectra of high-density InGaAs/AlGaAs quantum wire structures

We investigated the temperature dependence of the time-resolved photoluminescence (PL) spectra of high-density InGaAs/AlGaAs quantum wire (QWR) distributed-feedback laser structure on a submicron grating. A red-shift of peak in the time-resolved PL after photo-excitation was observed due to the relaxation of the photo-generated excitons from the entire QWR to localized centers at 10 K. On the other hand, at 60 K, no red-shift in the time-resolved PL spectra was observed since the localization centers are thermally activated and the excitons are delocalized.     

激光大气等离子体时间演化特性的光谱研究

采用延时光谱法和谱线演化法 ,对YAG脉冲激光器 1 0 6 μm光束击穿一个大气压的空气所产生的等离子体进行了时间分辨光谱研究。对激光大气等离子体连续光谱的短波带与长波带分别进行了时间分辨测量 ,结果表明两者的衰变速率均在等离子体激发约 0 5微秒以后明显变慢。分析认为这种衰变速率的变慢可能与空气中氧对自由电子的吸附与去吸附有关。对激光大气等离子体线状光谱所作的时间分辨测量则表明 ,大部分线状光谱的演化寿命大于其标称寿命 ,部分线状光谱还呈现“衰变—增涨—衰变”的复杂形式。分析认为线状光谱的这些演化特征可能与等离子体在衰变期间的各种复合过程和能量转移过程有关。     

Structural changes in excited states and photoisomers determined by time-resolved Raman scattering

Molecules in the excited singlet and triplet state and photoproducts occuring after photoisomerization or proton transfer are investigated by time-resolved resonance Raman and resonance CARS spectroscopy with nanosecond time resolution. From the time-resolved spectra information on structures and bond strengths of these short-lived species and on their kinetics are obtained.     

Fe~(3+)对石墨烯氧化物荧光淬灭机理的研究

采用改进的Humer法合成了石墨烯氧化物,利用搭建的时间分辨光谱探测系统详细探究了Fe~(3+)(浓度为0.5、1、2 mmol/L)对石墨烯氧化物荧光淬灭物理机制。稳态荧光发射光谱中,随着Fe~(3+)浓度的增加,石墨烯氧化物的荧光强度急剧减弱。时间分辨荧光光谱和飞秒瞬态吸收光谱研究证实,加入不同浓度Fe~(3+)的GO其动力学衰减曲线基本没有任何变化。结果表明,Fe~(3+)对石墨烯氧化物的荧光淬灭主要是静态的荧光淬灭过程。     

0.23 eV energy resolution obtained using a cold field-emission gun and a streak imaging technique

We demonstrate that a high energy resolution of 0.23 eV is possible by using a cold field-emission electron gun (CFEG) without a monochromator. We have used a 300 kV transmission electron microscope (Hitachi, HF-3000) equipped with a CFEG and an energy filter (Gatan, GIF2002). Since energy instability is critical for high energy resolution in electron energy-loss spectroscopy, we have applied a high-speed 'streak imaging' acquisition technique, in which a series of time-resolved spectra are acquired as a two-dimensional spectrum. With this technique, we can easily record 1000-20,000 spectra with an exposure time of 0.353 ms per spectrum. Instability of less than 1.4 kHz has been corrected in the time-resolved spectra, allowing the inherent performance of the CFEG to be realized.     

机油类产品激光诱导荧光时间特性的研究

介绍了一种由三倍频Nd∶YAG激光器、单色仪、光电倍增管以及信号采集处理系统构成的激光荧光谱寿命测量系统及其测量原理和方法,讨论了如何去除激发光脉冲宽度和探测系统响应速度对测量结果的影响,并实际测量了一种应用广泛的燕山机油的荧光谱寿命.本系统具有简便、快捷、准确以及成本低等优点,适合用于未来实用化机载水面监测激光荧光雷达遥感系统中 关键词： 激光诱导荧光 荧光寿命 Nd∶YAG激光器 光电倍增管     

激光等离子体软x光辐射的时间分辨测量

采用透射光栅和软x光条纹相机测量了铜激光等离子体软x光发射的时间分辨光谱。通过比较时间分辨谱和时间积分光谱,从实验上考查了条纹相机在软x光区域的响应特性。文中也给出了激光等离子体软x光不同谱带及波长发射的时间过程。     

激光等离子体X光辐射非平衡特性实验研究

在ＬＦ－１１和ＬＦ－１２高功率激光装置上进行的实验中，设计了一些特定的激光束－金腔靶－探测器条件，创造了激光直接加热、准辐射加热和激光、Ｘ光混合加热三种物理条件，采用软Ｘ光透射光栅能谱时空分辨技术，测量了腔靶、缝靶和双孔靶等高分辨Ｘ光能谱，研究了激光等离子体Ｘ光辐射非平衡特性。     

Optical measurements on semiconductor microcrystal beams generated by gas evaporation

We have developed a simple measurement method for measuring the optical spectra of free microcrystals, by combining the time-resolved and space-resolved spectroscopies with the gas evaporation method. The structure of the obtained spectra and their time- and space-dependencies indicate well the quantum-confinement effects of carriers and excitons in free semiconductors microcrystals.     

稀土荧光螯合物时间分辨荧光光谱分析方法研究

以提高固相时间分辨荧光免疫分析灵敏度为目的,在自行研制固相时间分辨荧光免疫分析样机和合成新荧光化合物的基础上,首先对新合成的4,4'-二溴-6,6'-二(N,N-二(乙氧基羰基)氨甲基)-2,2'-联吡啶-Eu(Ⅲ)螯合物的荧光性质及时间分辨荧光光谱分析方法进行了研究;其次对Eu-TTA-phen和Eu-β-NTA-TOPO等化合物进行时间分辨荧光光谱分析检测.     

磷光染料掺杂有机分子发光的能量转移研究

用稳态光谱和时间分辨的超快光谱研究了不同浓度磷光染料PtOEP掺杂有机小分子Alq薄膜的发光特性和能量转移.据PtOEP的吸收光谱与Alq的荧光光谱,用Frster理论估算出Alq:PtOEP掺杂体系的能量转移临界半径及其转移效率.稳态荧光光谱显示,在Alq:PtOEP掺杂薄膜中,随着掺杂浓度的升高,PtOEP的发光强度增强,Alq的发光强度逐渐减弱,两者间的能量转移效率与理论计算结果一致.利用时间分辨光谱研究了Alq:PtOEP掺杂薄膜体系的能量转移动力学过程,观察到Alq:PtOEP掺杂薄膜的荧光寿 关键词： 有机掺杂薄膜 稳态光谱 时间分辨光谱 能量转移     

Luminescence and electronic excitations in KBe<Subscript>2</Subscript>BO<Subscript>3</Subscript>F<Subscript>2</Subscript> crystals

This paper reports on a study of the dynamics of electronic excitations in KBe₂BO₃F₂ (KBBF) crystals by low-temperature luminescent vacuum ultraviolet spectroscopy with nanosecond time resolution under photoexcitation by synchrotron radiation. The first data have been obtained on the kinetics of photoluminescence (PL) decay, time-resolved PL spectra, time-resolved PL excitation spectra, and reflection spectra at 7 K; the estimation has been performed for the band gap E _g = 10.6−11.0 eV; the predominantly excitonic mechanism for PL excitation at 3.88 eV has been identified; and defect luminescence bands at 3.03 and 4.30 eV have been revealed. The channels of generation and decay of electronic excitations in KBBF crystals have been discussed.     

Analysis of time-resolved CW-EPR spectra of short-lived radicals at different times after laser excitation

Laser excitation combined with time-resolved CW-EPR spectroscopy of a carotenoid-porphyrin-diquinone tetrad (1), observes polarized spectra of the end quinone radical anion, Q·_B ^?. These spectra strongly depend on the time interval between the laser pulse and the position of the detection window of the transient magnetization profile, and may lead to misinterpretation of the radical intermediates participating in the reaction route. Spectral distortions arise from small hyperfine splittings and narrow line widths, resulting in the appearance of Torrey wiggles at off-resonance fields. The correct spectrum, however, and its line shape appear at times above 1 μs after the laser pulse, and is in complete agreement with the Fourier transform EPR spectrum. Analysis and reconstruction of the transient spectra is carried out in Fourier conjugate space. The experimental spectra are shown to be the Fourier transform of the free-induction decay (FID) multiplied by an appropriate windowing function. The changes in the spectra taken at t<1 μs are due to line distortions and not to chemical processes. This treatment is of general applicability in the spectral analysis of time-resolved CW-EPR spectra.     

Spectroscopic and Photophysical Properties of Protonated Forms of Some Fluoroquinolones in Solutions

Electronic absorption and fluorescence spectra of ciprofloxacin, norfloxacin, enoxacin, pefloxacin and nalidixic acid in aqueous solutions were investigated. The time-resolved fluorescence spectra were measured and interpreted. The changes of the luminescence spectra and electron structure of the compounds under study are explained by different degrees of the spin-orbital interaction caused by nitrogen heteroatoms lone pairs effect. Possible ways of the protonation process for naphtyridine and quinolone rings with different substitutions are discussed. The photophysical behavior of FQs was studied using density functional theory (DFT) calculations.     

Simulation of time-resolved vibronic spectra and the possibility of analyzing molecules with similar spectral properties

The possibility of using time-resolved vibronic spectroscopy for spectral analysis of mixtures of chemical compounds with similar optical properties, when traditional methods (based on stedy-state spectra) are inefficient, is demonstrated by using the method of computer simulation. The analysis is carried out by the example of molecules of a series of polyenes (butadiene, hexadiene, octatetraene, decapentaene, and decatetraene), their various cis-and trans-rotational isomers, and phenyl-substituted polyenes. Ranges of relative concentrations of molecules similar in their spectral properties, where reliable interpretation of time-resolved spectra of mixtures and both qualitative and quantitative analyses are possible, are determined. The use of computer simulation methods for optimizing full-scale experiments in femtosecond spectroscopy is shown to hold much promise.