Analysis of the composition and structure of aqueous media under excitation by lasers and light emitting diodes

We developed a method for detecting traces of foreign components in water and analyzing the microstructure of water. The method is based on studies of the characteristics of secondary emission arising in aqueous media under excitation by radiation of ultraviolet lasers and light emitting diodes. A new type of cuvette (capillary cuvettes) for studying the secondary emission in molecular media was elaborated. The cuvettes enable the study of aqueous solutions at small concentrations of the components; they enable one to recognize the type of molecular compound present in aqueous media, in view of the photoluminescence spectra.     

Photoluminescence of aromatic compounds in photon traps under resonant pulse-periodic excitation

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.     

Photoluminescence of traces of aromatic compounds in aqueous solutions upon excitation by a repetitively pulsed laser

A method is suggested for quantitative and qualitative analysis of aromatic compounds in water at extremely low concentrations (<1 ng/l). The method is based on excitation of luminescence by short (20 ns) UV laser pulses with a peak power of 10⁴ W at 255.3 nm and a pulse repetition rate of 10 kHz. The shape of luminescence spectra of benzene, benzoic acid, saccharin, aspirin, and L-tryptophan at low concentrations in water is analyzed. The luminescence kinetics of these compounds is studied at short delay times (10–20 ns). The lifetimes of the electronic excited states of the aromatic compounds are measured. The applications of the method for studies of low-concentration aqueous solutions of biological and medicine compounds are analyzed.     

Study of the interaction of antigens and antibodies by photoluminescence spectra excited by ultraviolet laser radiation

Photoluminescence spectra of isotonic solutions of antigens, i.e., “Taeniarhynchus saginatus” (polysaccharide) larvae and aqueous solutions of antibodies to them, extracted from calf blood serum are measured. Photoluminescence spectra were excited by ultraviolet radiation (266 nm) of the fourth harmonic of the yttrium aluminum garnet laser. The spectra of these objects are strong bands with intensity maxima at wavelengths of 341 and 332 nm for serum and polysaccharide, respectively. It was found that mixing of polysaccharide and serum solutions in a ratio 1:6 results in a drastic decrease in the photoluminescence intensity spectrum, which indicates bonding of corresponding molecular structures.     

稀土氟碳酸盐矿物的光致发光谱和吸收谱研究

测定并讨论了产自四川冕宁矿区的氟碳铈矿和产自内蒙白云鄂博稀土矿区的黄河矿、氟碳钙铈矿、氟碳铈钡矿的光致发光谱。结果表明,稀土氟碳酸盐矿物在488.0nm和514.5nm激光激发下的光致发光中心是Nd3+,发光谱中的所有谱带均出自Nd3+的辐射跃迁。在488.0nm激光激发下,稀土氟碳酸盐矿物在495nm到733nm谱区的发光谱带强而尖锐,但在514.5nm激光激发下,这个谱区的谱带明显变弱或消失,转而出现783nm到907nm谱区的强发光谱带。可见光吸收谱表明稀土氟碳酸盐矿物对可见光的吸收也与矿物中的Nd3+有关。     

Sensitized UV luminescence from single crystals of zinc oxide

The reflection, absorption, excitation, photoluminescence, and cathodoluminescence spectra have been studied for indium-doped single crystals of ZnO. The temperature quenching of the UV-radiation bands has also been studied. These studies have made it possible to establish that the UV-radiation bands are excited during quantum absorption corresponding to “band-band” transitions and also by exciton absorption. The studies have also made it possible to calculate the activation energy of the temperature quenching. In the photoluminescence spectrum of ZnO crystals there is a wide radiation band in the 3950–4050-Å region which could be described by transitions in donor-acceptor pairs. It is shown that the band of the equidistant series at 3834 Å is complex in character.     

Spectral Properties of CuGaxIn1−xSe2 Solid Solutions

We have investigated the absorption spectra in the region of the fundamental absorption band edge and the photoluminescence spectra of single crystals of the ternary compounds CuInSe₂ and CuGaS₂, and of solid solutions based on them that were grown by the method of chemical transport reaction. The forbidden band width and the positions of the maxima of the radiation bands are determined. The concentration dependences of the indicated quantities are plotted and they are shown to be linear.     

Electronic excitations and luminescence of SrMgF4 single crystals

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.     

Luminescence centers in phosphorus-doped Cd1−xMgxTe mixed crystals

The emission and excitation spectra of P-doped Cd_1?xMg_xTe (x ? 0.45) mixed crystals have been measured over the temperature range of 300 ～ 4.2 K to reinvestigate the photoluminescence process of two broad emission bands; the 690 nm band of the as- grown crystals and the 610 nm band of the annealed crystal. The excitation spectrum of each band has a characteristic peak at 550 nm near the absorption edge of this crystal. Together with the data of the decay characteristic and the halfwidth of each band, we discuss the difference in the recombination process when the crystal is excited under two different radiation at 365 and 570 nm (close to the 550 nm radiation). It is concluded that both emission bands arise from donor-acceptor pairs and a localized center or self- activated center; the associated pair is V_Cd-interstitial P in the as-grown and V_Te ? P_Te in the annealed crystal.     

Raman scattering and photoluminescence in sodium uranyl acetate polycrystals

A technique of probe photoluminescence and Raman spectroscopy has been developed. This technique makes it possible to detect small (10^?6 to 10^?8 g) amounts of uranyl compounds at short exposure times (1?10 s). The photoluminescence spectra of Na[UO₂CH₃(COO)₃] polycrystals recorded upon excitation by short-wavelength radiation of LEDs and lasers are found to contain equidistant bands with a shift of 854 cm^?1, which corresponds to the frequency of totally symmetric uranyl vibration also manifesting itself in Raman spectra.     

双背景法扣除溶剂水峰及蛋白质热变性的研究

研究蛋白质水溶液的红外光谱(IR)谱时,由于溶剂水的强吸收与蛋白质的吸收峰会发生严重重叠,极大地干扰对蛋白质吸收峰的识别、定性、定量和结构分析.尝试利用杂化光谱法扣除溶剂水峰.采用双背景方法,用空白ATR晶体(背景样品1)与ATR水层(背景样品2)合成了单光束杂化背景谱,通过控制对背景样品1和背景样品2的扫描次数,合成...     

Investigation of luminescence processes in YAG single crystals irradiated by 50 MeV electron beam

Absorption, emission and excitation spectra of 50 MeV electron beam irradiated and as-grown YAG single crystals were studied and compared in the 10–300 K temperature range using time-resolved luminescence spectroscopy under UV/VUV/XUV excitation by synchrotron radiation and cathodoluminescence. The emission spectra consist of intrinsic (excitonic) and defect related non-elementary bands in the VIS/UV range. It is shown that fast electrons create stable F and F⁺ color centers with characteristic emission and absorption bands in the visible/UV range. Induced absorption caused from these defects starts at 4.2 eV. Energy transfer from host to color centers is not an efficient process.     

富勒烯有机溶液光致荧光研究

本文研究了C60、C70有机溶液的荧光效应,发现它们的Pyridine溶液在可见和紫外激光激发下有强而且宽的荧光峰,两种分子的吸收谱和荧光谱具有特殊的互补性,其混合物可以实现红绿蓝三色光致发光,体现了富勒烯在白光有机光致发光材料开发方面的潜在价值。     

Raman scattering and luminescence of yttria nanopowders and ceramics

We have studied Raman scattering in yttria nanopowders and ceramics that was excited by radiation at wavelengths of 514.5 and 632.8 nm. We show that, in undoped nanopowders and cubic phase of doped yttria ceramics, only the Raman scattering by phonons is observed, with no other Raman scattering centers having been revealed. In nanopowders of the monoclinic phase, we have observed an additional Raman line with a Raman shift of 1093 ± 4 cm^?1. If all the objects under investigation are excited by the radiation at a wavelength of 514.5 nm, their spectra exhibit four series of photoluminescence lines, two of which (at λ = 521–523 and 538–564 nm) are emitted by Er³⁺ ions, “impurity” dopants, while the other two lines (at λ = 607–635 and 644–684 nm) are emitted by intrinsic centers. Under excitation by the radiation at a wavelength of 632.8 nm, only a series of bands at λ = 644–684 nm is emitted. In addition to these photoluminescence bands, neodymium-doped ceramics show photoluminescence bands of Nd³⁺ ions. We have shown that intrinsic luminescence centers, which occur in all the examined specimens, are capable of acting as acceptors with respect to neodymium ions excited to the upper laser level.     

Fluorescent probe based on proton transfer in 4′-(diethylamino)-3-hydroxyflavone: Spectral and luminescent characteristics upon selective excitation

The spectral characteristics of acetonitrile solutions of 4′-(diethylamino)-3-hydroxyflavone dye with dual fluorescence are studied under selective excitation. This dye is a structural analog of 3-hydroxyflavone and exhibits excited-state proton transfer, which, in contrast to 3-hydroxyflavone, has a thermodynamic rather than a kinetic character. The fluorescence spectra at different excitation photon energies and the excitation spectra of different fluorescence bands are studied. It is found that the intensity ratio of the normal and tautomeric fluorescence bands lying near 507 and 570 nm, respectively, depends on the excitation wavelength, namely, this ratio is 1.45 and almost does not change in the region of the main absorption band (370–420 nm), while, in the region of the second singlet band (near 280 nm), it decreases to 1.15. This can be explained by an increase in the probability of proton transfer with formation of a tautomeric form in the case of excitation into the second band. Another interesting feature is the existence of a latent third emission band peaked at 535 nm, which was found and reliably recorded upon excitation at wavelengths of 470–500 nm. Addition of water quenches this emission, which indicates that it belongs to the anionic form of the dye.     

Electron excitations in LiB3O5 crystals with defects: Low-temperature time-resolved luminescence VUV spectroscopy

The dynamics of electron excitations and luminescence of LiB₃O₅ (LBO) single crystals was studied using low-temperature luminescence vacuum ultraviolet spectroscopy with a subnanosecond time resolution under photoexcitation with synchrotron radiation. The kinetics of the photoluminescence (PL) decay, the time-resolved PL emission spectra, and the time-resolved PL excitation spectra of LBO were measured at 7 and 290 K, respectively. The PL emission bands peaking at 2.7 eV and 3.3 eV were attributed to the radiative transitions of electronic excitations connected with lattice defects of LBO. The intrinsic PL emission bands at 3.6 and 4.2 eV were associated with the radiative annihilation of two kinds of self-trapped electron excitations in LBO. The processes responsible for the formation of localized electron excitations in LBO were discussed and compared with those taking place in wide-gap oxides.     

Excitation spectra and structure of luminescence centers of manganese ions in single crystals of zinc sulfide

We investigate the photoluminescence excitation spectra in ZnS:Mn single crystals at room temperature and at the temperature of liquid nitrogen with a different concentration of Mn²⁺ ions. The strongest bands peaking at 557, 578, 600, and 637 nm are associated with a different position of the Mn ion in the lattice of the crystals under investigation. The difference obtained in the excitation spectra can be explained by the resonance transfer of energy between the Mn ions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 208–210, March–April, 2000.     

Dy3+激活无水芒硝在真空紫外光激发下的发光性质

在空气中900℃温度下,将纯天然无水芒硝( Na2 SO4)和DyF3的混合粉末加热25 min,制备了Na2SO4:Dy3+新型发光材料.通过同步辐射研究了NaSO4:Dy3+的发光性质.并测量了在室温中真空紫外-紫外光下的发射和激发光谱.根据发射光谱得到了不同Dy3+掺杂浓度和不同激发下发光的黄蓝比(Y/B)是不同的.通过监测黄色发光得到的激发光谱,分别由Dy3+,4f9→4f85d跃迁(172 nm)、O2--Tm3+之间的电荷转移带(165 nm)引起的强激发谱和基质吸收(138,245 nm)、对应Dy3+,6 H15/2→4 D7/2,6H15/2→6 P3/2,6 H15/2→6P7/2跃迁(299,325,351nm)引起的弱激发谱组成.