共查询到20条相似文献,搜索用时 31 毫秒
1.
R. A. Bisengaliev É. D. Batyrev B. V. Novikov A. V. Sel’kin 《Physics of the Solid State》1998,40(5):806-807
The exciton photoreflection spectra of CdS crystals are studied. It is found that the form of the exciton photoreflection
spectrum is determined by a Stark shift of the exciton energy in the electric field of surface states. The dependences of
the exciton photoreflection spectrum on temperature on the intensity and wavelength of the modulating radiation, and on the
processes by which the photoreflection signal relaxes is determined. An energy scheme is proposed for the surface states which
explains the observed effects of photoinduced changes in the surface field. A correlation is established between the exciton
photoreflection spectrum and the form of the fine structure in the photoconductivity.
Fiz. Tverd. Tela (St. Petersburg) 40, 875–876 (May 1998) 相似文献
2.
V. A. Pustovarov I. N. Ogorodnikov S. I. Omelkov L. I. Isaenko A. P. Yelisseyev A. A. Goloshumova S. I. Lobanov P. G. Krinitsyn 《Physics of the Solid State》2014,56(3):456-467
The electronic and crystal structures of SrMgF4 single crystals grown by the Bridgman method have been investigated. The undoped SrMgF4 single crystals have been studied using low-temperature (T = 10 K) time-resolved fluorescence optical and vacuum ultraviolet spectroscopy under selective excitation by synchrotron radiation (3.7–36.0 eV). Based on the measured reflectivity spectra and calculated spectra of the optical constants, the following parameters of the electronic structure have been determined for the first time: the minimum energy of interband transitions E g = 12.55 eV, the position of the first exciton peak E n = 1 = 11.37 eV, the position of the maximum of the “exciton” luminescence excitation band at 10.7 eV, and the position of the fundamental absorption edge at 10.3 eV. It has been found that photoluminescence excitation occurs predominantly in the region of the low-energy fundamental absorption edge of the crystal and that, at energies above E g , the energy transfer from the matrix to luminescence centers is inefficient. The exciton migration is the main excitation channel of photoluminescence bands at 2.6–3.3 and 3.3–4.2 eV. The direct photoexcitation is characteristic of photoluminescence from defects at 1.8–2.6 and 4.2–5.5 eV. 相似文献
3.
This study has been carried out using synchrotron radiation, time-resolved luminescence ultraviolet and vacuum ultraviolet spectroscopy, optical absorption spectroscopy, and thermal activation spectroscopy. It has been found that, in scintillation spectrometric crystals LaBr3: Ce,Hf characterized by a low hygroscopicity, along with Ce3+ centers in regular lattice sites, there are Ce3+ centers located in the vicinity of the defects of the crystal structure. It has also been found that the studied crystals exhibit photoluminescence (PL) of new point defects responsible for a broad band at wavelengths of 500–600 nm in the PL spectra. The minimum energy of interband transitions in LaBr3 is estimated as E g ~ 6.2 eV. The effect of multiplication of electronic excitations has been observed in the range of PL excitation energies higher than 13 eV (more than 2E g ). Thermal activation studies have revealed channels of electronic excitation energy transfer to Ce3+ impurity centers. 相似文献
4.
5.
利用紫外CCD光学多道分析器,测量了云覆盖条件下的太阳紫外辐射光谱,着重研究了云对太阳紫外辐射光谱的影响.光谱分析结果表明,太阳紫外辐射光谱强度受云的影响而衰减:太阳紫外辐射光谱强度衰减依赖于波长,且随波长的递减而减小;云量越大,衰减越强;波长在315 nm以下波段的太阳紫外辐射光谱强度受云影响相对较小.研究结果有较重... 相似文献
6.
Dingshan Yu Yujie Chen Baojun Li Fuli Zhao Cairong Ding Xudong Chen 《Applied Physics A: Materials Science & Processing》2011,103(2):329-334
We have demonstrated catalyst-free fabrication of multi-branched ZnO nanorods and their interesting optical properties. Under
Xe lamp excitation (325 nm), it is found that the ethanol rinsing leads to an obviously enhanced ultraviolet emission at room
temperature. Moreover, temperature-dependent emission spectra exhibit an anomalous temperature dependence of the ultraviolet
emission intensity. This has been analyzed in terms of the competition between the radiative and nonradiative hopping processes
using a model developed for disordered porous semiconductors. With femtosecond pulse excitation (640 nm), two-photon-induced
photoluminescence is observed, which is confirmed by the quadratic dependence of the emission intensity on the excitation
pulse energy. 相似文献
7.
The induced photoluminescence (PL) from the π-conjugated polymer poly allyl diglycol carbonate (PADC) (CR-39) upon excitation with the ultraviolet radiation of different wavelengths was investigated. The absorption and attenuation coefficients of PADC (CR-39) were recorded using a UV–visible spectrometer. It was found that the absorption and attenuation coefficients of the PADC (CR-39) exhibit a strong dependence on the wavelength of ultraviolet radiation. The PL spectra were measured with a Flormax-4 spectrofluorometer (Horiba). PADC (CR-39) samples were excited by ultraviolet radiation with wavelengths in the range from 260 to 420 nm and the corresponding PL emission bands were recorded. The obtained results show a strong correlation between the PL and the excitation wavelength of ultraviolet radiation. The position of the fluorescence emission band peak was red shifted starting from 300 nm, which was increased with the increase in the excitation wavelength. The PL yield and its band peak height were increased with the increase in the excitation wavelength till 290 nm, thereafter they decreased exponentially with the increase in the ultraviolet radiation wavelength. These new findings should be considered carefully during the use of the PADC (CR-39) in the scientific applications and in using PADC (CR-39) in eyeglasses. 相似文献
8.
金纳米颗粒的紫外、蓝紫光波段光致荧光特性 总被引:4,自引:1,他引:3
采用电化学方法制备出粒径在20~30 nm的悬浮胶体金纳米颗粒。研究了金纳米颗粒的荧光发射光谱特性。在377和459 nm观察到两个荧光发射峰,分别位于紫外和蓝紫光波段,对应的敏感激发波长为220 nm。减小激发光强度或降低金纳米颗粒的粒子数密度都会使377 nm处的荧光发射峰强度减弱。位于459 nm处的荧光发射峰对激发光强度和颗粒数密度变化更为敏感,并且在激发光强度降低到一定阈值或粒子数密度高于一定阈值后消失。随着激发光强度的增加,位于377和459 nm处的两发射峰强度逐渐靠近,其比值逼近于1。实验结果与随机分布介质的自组织散射式谐振腔理论符合得较好。这表明胶体金纳米颗粒中存在循环多重散射,并由此引发了蓝光及紫外波段的荧光增强,这在光存储和全色显示等方面具有潜在的应用前景。 相似文献
9.
Experimental studies of Raman scattering and the infrared reflection spectra of lithium tetraborate crystals were carried out within a broad temperature range with various polarization geometries. The crystals studied are characterized by record values of radiation resistance, transparence within a broad spectral range including the ultraviolet region, and nonlinear optical properties. A group-theoretical analysis of the vibrational spectra of this crystal was performed and fundamental vibrational terms were assigned to the symmetry types of the point group as well as the polarizations of the corresponding modes. The effective Raman cross section was measured and was found to be one order of magnitude higher than those of the known crystals, in which the stimulated Raman scattering (SRS) was observed. The nonlinear optical and electrooptical coefficients were evaluated and were found to be consistent with the results of independent measurements. The effect of a drastic increase in the intensity of quasi-elastic light scattering at 253 K was registered. It was associated with the phase transition that consists of the disordering of lithium ions with respect to the rigid skeleton. The formation energy for Frenkel defects in the lithium sublattice and the activation energy of the ionic conduction when heating the sample were calculated from the obtained temperature dependences of the intensity of quasielastic and hyper-Rayleigh light scattering. 相似文献
10.
Several luminescence properties of acetylated cellulose were studied as functions of the ester group concentration and of the wavelength of the exciting radiation. Of the three luminescence bands arising on irradiation at specific wavelengths, the ultraviolet band has a structure. A correlation was established between the intensity of this band and the ester group content, as well as a qualitative similarity between the luminescence excitation spectra and the absorption spectra. The relative quantum yield of the luminescence depends on the wavelength of the excited radiation. It is proposed that the centers which are specific for the ultraviolet luminescence are acetyl groups of two different types. 相似文献
11.
不同波长激发光对血清荧光光谱影响的实验研究 总被引:2,自引:0,他引:2
采用日本岛津荧光光度计RF5301,研究了血清的荧光光谱与激发光波长的关系。实验结果表明:在不同波长的紫外光激励下,血清产生的荧光光谱线型及峰值波长基本相同,与激励光波长无关,但荧光峰强度随激励光波长变化而变化。血清的荧光光谱有两个较强的荧光发射区,其中第一个发射区处于300~410 nm,第二个发射区处于410~530 nm。当激发光波长小于310 nm,荧光主要集中在第一发射区,荧光峰位于330和370 nm处,并产生竞争现象。当激发光波长大于250 nm时,只出现330 nm处的荧光峰,其最佳激励光波长为300 nm;当激发光波长大于320 nm,第一发射区的荧光变弱,在第二发射区的荧光变强,荧光峰位于452 nm。此研究为血液的光谱特性研究提供了实验依据,对光诱导荧光光谱诊断技术中激发光波长的选择具有一定的参考价值。 相似文献
12.
The temperature dependence of the integrated photoluminescence intensity of nanometer-sized ZnTe/CdTe/ZnTe quantum wells has
been investigated under different excitation conditions. It has been shown that the character of thermal decay of the luminescence
intensity depends on the frequency of the exciting light and, under the above-barrier excitation, strongly depends on the
optical excitation power density. It has been found that an increase in the excitation intensity leads to a saturation of
thermal quenching of the luminescence in the low-temperature range. The conclusion has been drawn that this behavior reflects
the saturation of nonradiative recombination centers with photoexcited carriers. 相似文献
13.
蒽(anthracene)具有良好的热稳定性以及较高的荧光量子产率的优点, 是最早用于研究有机发光器件(organic light-emitting device, OLED)的材料之一. 在本文中, 主要利用量子化学方法研究了不同外电场对蒽分子激发特性的影响规律. 首先采用密度泛函理论(density functional theory, DFT)在6-311G(d, p)基组水平上对蒽分子基态结构进行优化, 基于稳定基态结构, 利用含时密度泛函(time-dependent density functional theory, TDDFT)以及同一基组水平, 计算出蒽分子的前十个激发态的激发能、跃迁偶极矩、振子强度和紫外吸收光谱等数据. 然后以密度泛函B3P86方法优化出的不同外电场下蒽分子基态结构为基础, 使用TDDFT方法研究了不同外电场对蒽分子前线轨道能级和激发特性的影响规律. 结果显示, 无场时蒽分子在紫外区域234.50 nm处有一个较强的吸收峰, 对应基态电子跃迁至第5激发态吸收光子波长; 在外电场作用下, 蒽分子电子由基态跃迁到激发态的各项光谱参数均有显著变化, 加场后蒽分子的吸收光谱发生了红移, 由紫外波段移向了紫外–可见光波段, 与实验值相符合. 分子前线轨道的计算结果也表明蒽分子的最高占据轨道(highest occupied molecular orbital, HOMO)和最低未占据轨道(lowest unoccupied molecular orbital, LUMO)能量差值在不同电场下存在差异.
关键词:
蒽
外电场
激发特性 相似文献
14.
A. V. Larionov V. B. Timofeev J. Hvam K. Soerensen 《Journal of Experimental and Theoretical Physics》2000,90(6):1093-1104
Luminescence spectra of interwell excitons in GaAs/AlGaAs double quantum wells with electric-field-tilted bands (n-i-n) structures were studied. In these structures the electron and the hole in the interwell exciton are spatially separated between neighboring quantum wells by a narrow AlAs barrier. Under resonant excitation by circularly polarized light the luminescence line of the interwell excitons exhibited appreciable narrowing as their concentration increased and the degree of circular polarization of the photoluminescence increased substantially. Under resonant excitation by linearly polarized light the alignment of the interwell excitons increased as a threshold process with increasing optical pumping. By analyzing time-resolved spectra and the kinetics of the photoluminescence intensity under pulsed excitation it was established that under these conditions the rate of radiative recombination increases substantially. The observed effect occurs at below-critical temperatures and is interpreted in terms of the collective behavior of the interwell excitons. Studies of the luminescence spectra in a magnetic field showed that the collective exciton phase is dielectric and in this phase the interwell excitons retain their individual properties. 相似文献
15.
16.
Yu. D. Khamchukov V. V. Klubovich A. V. Myasoedov S. N. Shashkov 《Journal of Applied Spectroscopy》1999,66(2):233-239
For single crystal wafers of lead germanate cut perpendicularly to the C-axis an investigation has been made of IR transmission
and RS spectra atλ
exc
=632.8, 514.5, and 488 nm in the spectral range of 400–1800 cm−1. An interpretation of the spectra recorded is suggested. In the RS spectra specific features of line intensity distributions
are detected. The dependences of the intensity distribution in the peculiarities detected on the excitation wavelength and
the angle of incidence of exciting radiation and transmission of the reflected exciting laser beam relative to the optical
axis of illumination of the spectrometer inlet slit are investigated. The reason for the occurrence of these specific features
is suggested: the interference of RS radiation and exciting laser radiation diffracted on the non-working narrow sides of
the diffraction gratings of the spectrometer. The possibilities of amplifying the spectral lines in the RS spectra by imposing
diffracted one-mode exciting radiation on them are discussed.
Translated from zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 220–226, March–April, 1999. 相似文献
17.
Yu. P. Voinov V. S. Gorelik A. Yu. Pyatyshev M. F. Umarov 《Bulletin of the Lebedev Physics Institute》2012,39(12):341-346
The photoluminescence spectra of aromatic compounds in a photon trap under ultraviolet pulse-periodic excitation are recorded. It is shown that the photoluminescence spectrum shape depends on the material layer thickness in a cell, physical state of the sample, and exciting radiation characteristics: as the layer thicknesses decreases, the intensity is significantly redistributed, which is explained by the transition from spontaneous luminescence to superluminescence. 相似文献
18.
A. G. Milekhin N. A. Yeryukov L. L. Sveshnikova T. A. Duda E. I. Zenkevich S. S. Kosolobov A. V. Latyshev C. Himcinski N. V. Surovtsev S. V. Adichtchev Zhe Chuan Feng Chia Cheng Wu Dong Sing Wuu D. R. T. Zahn 《Journal of Experimental and Theoretical Physics》2011,113(6):983-991
Raman scattering (including nonresonant, resonant, and surface enhanced scattering) of light by optical and surface phonons of ZnO nanocrystals and nanorods has been investigated. It has been found that the nonresonant and resonant Raman scattering spectra of the nanostructures exhibit typical vibrational modes, E 2(high) and A 1(LO), respectively, which are allowed by the selection rules. The deposition of silver nanoclusters on the surface of nanostructures leads either to an abrupt increase in the intensity (by a factor of 103) of Raman scattering of light by surface optical phonons or to the appearance of new surface modes, which indicates the observation of the phenomenon of surface enhanced Raman light scattering. It has been demonstrated that the frequencies of surface optical phonon modes of the studied nanostructures are in good agreement with the theoretical values obtained from calculations performed within the effective dielectric function model. 相似文献
19.
V. G. Kravets 《Optics and Spectroscopy》2005,98(3):405-410
The spectra of reflection and magnetoreflection of light from the crystalline insulator α-Al2O3 in the IR spectral region (λ = 2.5–25 μm) are investigated. Some features in the magnetoreflection spectra in the wavelength range corresponding to the excitation of optical phonon modes in α-Al2O3 are found. A significant increase in magnetoreflection is observed near these wavelengths. The amplitude and shape of the magnetore-flection spectra for the p and s polarizations of probe light are determined. It is shown that the optical and magneto-optical properties of α-Al2O3 in the IR region can be described on the basis of the theory of polaron excitation. A satisfactory correlation between the theoretical and experimental spectra is obtained, which indicates that polarons play an important role in determining the optical characteristics of nonmagnetic insulators and make the dominant contribution to the magnetoreflection spectra. 相似文献
20.
The effect of two-photon absorption and optical excitation area on the generation of THz radiation 总被引:1,自引:0,他引:1
It was found experimentally that the THz radiation throughput based on optical rectification is strongly related to the optical excitation size in a ZeTe emitter. The factors affecting the THz radiation throughput are investigated in detail both experimentally and theoretically. By taking into account optical rectification, diffraction and two-photon absorption effects, a theoretical model is established to describe the emitting field intensity of THz radiation. There is excellent agreement between the theoretical results and the experimental data under high excitation power. Both theoretical and experimental results demonstrate that there is a trade-off between these three effects for THz radiation, and that in order to increase the THz radiation throughput based on optical rectification, one should choose suitable excitation size under a given pump power. 相似文献