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1.
The special features of the photoluminescence of the n +ni submicron structures of gallium arsenide are investigated. It is found that the character of the dependence of the fluorescence intensity on the thickness of the structure is determined by the relationship between three characteristic lengths: diffusional length, thickness of the n + layer, and depth of absorption of exciting radiation, whereas the decrease in the mobility of charge carriers in epitaxial layers leads to an increase in the fluorescence intensity of the structure, with exciting radiation being strongly absorbed.  相似文献   

2.
The influences of thermal treatment on cold crystallization and the thermal behavior of poly‐L‐lactide (PLLA) were investigated by DSC and polarizing microscopy. Both the cooling and heating rates had effects on cold crystallization. Double peaks were observed for the samples on subsequently heating at 10°C min?1 after cooling between 5 and 20°C min?1. The degrees of crystallinity dramatically increased with decreasing cooling rate, and the size of PLLA spherulites increased with a decrease in the cooling rate. Double cold crystallization peaks were also observed during heating traces at higher rates for this material after fast cooling (20°C min?1) from the melt. The competition between the crystallization from the nuclei formed during cooling, and that from spontaneous nucleation might be responsible for the appearance of double peaks.  相似文献   

3.
《光谱学快报》2013,46(5-6):537-550
The vibrational frequencies of N‐acetyl‐L‐alanine (NAAL), its potassium salt (NAALK) and its free anionic form (NAAL?) are calculated using density functional theory (B3LYP) combined with the 6‐311 + + G(d,p) basis set. The experimental Raman spectrum of solid NAALK and the scaling factors for calculated values are discussed as well. The three species are characterized by intramolecular NH…O hydrogen bonds leading to the formation of a five‐membered ring. As indicated by the intramolecular (N)H…O distances and by the ν(NH) frequencies, the strength of the intramolecular hydrogen bond is ordered as follows: NAAL? < NAALK < NAAL?. Owing to their difference in the coupling with other vibrational modes, the in‐plane and out‐of‐plane vibrations do not reflect the strength of the hydrogen bond.  相似文献   

4.
The structure of thin films of Zntetraoctylphenylporphyrin (ZnTOPP) obtained by the spinning method is investigated. The kinetics of the decay of the fluorescence anisotropy of the films is analyzed in the form of a sum of exponents and by simulating the orientation of ZnTOPP complexes on the substrate (quartz) surface with allowance for the processes of the electron excitation energy transfer. The ZnTOPP films have a lamellar structure where individual layers form ordered domains. Within a domain, linear nonintersecting stacks of molecules are formed. In each stack the planes of the molecules are collinear, oriented perpendicularly to the surface of the substrate base, and form an angle of 45° with the directing axis of a stack.  相似文献   

5.
Based on a solution of the stationary modified Bloch equations, an investigation is made of the influence of the effect of internal optical bistability (IOB) on the behavior of the refractive index of a dense resonance medium as a function of the constant b of closerange dipoledipole interactions, frequency detuning, and the intensity of optical radiation. The conditions of existence of the IOB effect of the system dense resonance medium + optical radiation are found and the dynamics of the loop width of the hysteresis dependence of the population difference of the resonance levels of the medium on the characteristics of the system is traced. The domains of the parameters are determined in which the effects of selffocusing and selfdefocusing of the radiation propagating in a dense resonance medium can take place.  相似文献   

6.
The opticalcapacitance spectroscopy method and the means for its implementation are described. The results of experimental investigations of semiconductors are compared with the known data obtained by other methods. The information potentialities and advantages of the opticalcapacitance spectroscopy are shown.  相似文献   

7.
We shall focus on extended defect systems and review their critical behavior. Primarily, with two aims, one of which is to understand phase transitions and how to derive effective dimension of extended defects with various structures, and the other is to propose a new research-method for defect systems, we let extended defects grow on a triangular lattice with frustration in a similar fashion to diffusion-limited aggregation, and discuss the situation. The existence of phase transitions, phase diagram, effective defect dimension, etc. will be shown. Furthermore, we shall summarize theoretical studies of extended defect systems on phase diagrams, critical behavior, tricritical behavior, and crossover behavior as static properties, and on nonconserved systems and conserved systems as dynamic properties.  相似文献   

8.
The intramolecular hydrogen bond in steroid 5hydroxy6ketones and 5hydroxy6ketoximes of the stigmastane series has been investigated by the method of IR spectroscopy. It is shown that 5hydroxy groups in cisA/Bsteroids are linked by the intramolecular hydrogen bond with polar substituents at C3 and C6. These hydrogen bonds are lacking in corresponding transA/Bsteroids. According to the IR spectra, intramolecular associates of polymer type are formed in 5hydroxy6hydroxyminosteroids.  相似文献   

9.
Resonance Raman spectra (RRS) of Co(II) and Co(III)5,10,15,20tetrakis(4Nmethylpyridinium)porphyrin ((CoII(TmpyP4), and CoIII(TMPyP4)) in aqueous solutions at different pH as well as in organic solvents (methanol, ethanol, DMSO, DMF) are obtained. The increased sensitivity of the oscillation frequencies 2, 4, 8, and 6 — the markers of the oxidation state of a metal — to the nature of an axial ligand has been revealed. For CoIII(TmpyP4), the shifts of the indicated frequencies in extracoordination have turned out to be twofold larger than those for CoII(TmpyP4). The spectral effects observed are related to different electron influence of the extraligands on the system of the porphyrin ring. In the case of Co(III)porphyrin, interaction of the d orbitals of the metal and the e g *orbitals of the macrocycle is more efficient since its ionic radius is smaller than for the Co(II)complex. For CoIII(TmpyP4), a linear correlation between the oscillation frequencies 2, 4, 8, and 6 and the experimental Gutmann parameters characterizing the electronacceptor properties of solvents is found.  相似文献   

10.
The theory of intracavity parametric interaction of the components of Raman scattering is developed in the prescribedintensity approximation, which takes into account the reverse reaction of the excited waves to the pumpingwave phase. It is shown that one can substantially improve the conversion efficiency or the amplification coefficient of the antiStokes component by selection of the intracavity geometry, the optimum phase relation between the interacting waves, the pumping level, and the phase mismatch.  相似文献   

11.
The transverse distribution of the plasma temperature in the positive column of a d.c. cascade arc in argon at atmospheric pressure has been measured. The measurements have been carried out by the conventional method involving the determination of the emissivity of plasma as well as directly from the radiation spectrum of the arc without recourse to the Abelian inversion. A theoretical and model justification of the applicability of the second method is given. The results of the determination of the temperature profile in the observation direction by the width and shift of the ArI 425.9nm line selected for the diagnostics are presented. An analysis of the data obtained supports the possibility of determining the temperature of an inhomogeneous, optically thin plasma from the profiles of lines in the emission spectrum.  相似文献   

12.
Photodegradation of the reaction product of 1,2‐indanedione with glycine in methanol at room temperature has been studied using laser-induced fluorescence. Samples were liquid solution and developed fingerprints on papers. Continuous laser excitation of fresh solution of 1,2‐indanedione–glycine dissolved in methanol shows that the emission peak at 564 nm reached a quite stable low level after almost 1 hr of continuous excitation. For latent fingerprints on papers developed with 1,2‐indanedione dissolved in methanol solution, the luminescence peak decreases for the first week and reached a stable level for almost 2 weeks. A long‐term study is needed to reach a conclusion on the stability of the samples (liquid and developed fingerprints) at room temperature conditions.  相似文献   

13.
A procedure of xray spectral fluorescence analysis of the elemental composition of As x S100–x chalcogenide powder samples is developed and its metrological characteristics are established. In determining the content of the components in an As50S50 sample, the relative standard deviation was 0.0030 for As and 0.0035 for S. The results of the xray spectral fluorescence analysis are in good agreement with the data of a gravimetric method.  相似文献   

14.
《光谱学快报》2013,46(4):327-340
Electrospray/mass spectrometry ESI/MS analyses were performed to study the stability of calix[4]‐arene‐crown‐6/alkali cation complexes in the gas phase, and in acetonitrile/water mixtures. This approach allowed a comparison with previous investigations by molecular‐dynamic simulations,which demonstrated a complementarity between calculation and experiment. Experimental results obtained from ESI/MS confirm that the stability of calixarene/cation complexes depends upon the medium used. Indeed, the calixarene in solution presents a strong affinity for cesium, whereas in the gas phase, it has a stronger affinity for sodium. Similarly, the stability of [calixarene + Na]+‐type complexes in the solvent phase is increased by the presence of water in the dilution system (up to 40% in acetonitrile), whereas other alkaline complexes are destabilized by water in any proportion. Finally, calixarenes that bear benzo groups on their crowns have an affinity for sodium, which is weak in solution, but considerably stronger in the gas phase.  相似文献   

15.
We suggest a technique to control the rate of photocrosslinking fluorescent polymers by introducing a consumable acceptor of the energy of singlet excitation. We have constructed a model of the processes occurring in a layer of a photocrosslinking anthracenecontaining copolymer with the addition of the acceptor which is spent in the reaction of photooxidation by oxygen of the air and the algorithm for calculating the curves of gel formation in the presence of the acceptor. Comparison of the experimental kinetics of the depletion of the acceptor and accumulation of a gel in a layer with the data of model calculations has proved their good agreement. The possibility of increasing the contrast coefficient of the characteristic curve of negative photoresists on the basis of fluorescent photocrosslinked polymers with the aid of singlet excitation energy acceptors is demonstrated.  相似文献   

16.
The results of the investigation of the angular and spectralpolarization characteristics of 4501080nm radiation reflected from the surfaces of natural (leaves of trees, bark) and artificial (colored smooth surface, fabric) objects are discussed. Based on a study of the contrasts between these characteristics, we have determined the most informative spectralpolarization characteristics and the spectral and angular intervals the use of which in remote optical observations of objects would allow their most effective discrimination.  相似文献   

17.
An automated spectral complex for controlling the parameters of the plasmachemicalreactor working medium by the emission and absorption spectra in the 200–1100 and 2000–5000nm ranges has been developed. To record radiation, a CCD array and a pyroelectric detector are used. Control of the spectral device functions, data recording, and the obtaining of results reflecting the workingmedium parameters and the concentration in it of components being measured are carried out by means of a personal computer. The complex makes it possible to study the temporal behavior of the workingmedium parameters being measured with a resolution of up to 10–2 sec.  相似文献   

18.
A theoretical explanation is given to the experiments on Brewster reflection of light from the surface of certain liquids on the basis of the nearfield effects in a transitional layer. The consideration was carried out within the framework of the concept of a discretecontinuous dielectric in which the fields of the dipoles of discretely distributed atoms inside the Lorentz sphere surrounding the observation point are taken into account.  相似文献   

19.
Using the DFT/B3LYP method with the base set 631G**, we carried out calculation of the frequencies of the normal vibrations of porphin and of its five isotopic types. Scaling of force constants for outofplane vibrations has been performed in independent natural coordinates. The symmetry coordinates are introduced and a force field for outof plane vibrations of a porphin molecule in independent coordinates of symmetry is obtained. A new correlation of the frequencies of vibrations in the type of the symmetry B 1u for the isotopic type of the d 2 porphin molecule is suggested on the basis of discrete analysis of the distribution of a potential energy.  相似文献   

20.
Abstract

To investigate the in‐situ ordering process of isotactic polypropylene (iPP) from a melt state, a stationary growth front was prepared by the temperature slope crystallization (TSC) method. During the melt‐crystallization, iPP was crystallized into the α‐phase or β‐phase depending on the crystallizing conditions. The mechanism of the melt‐crystallization at the growth front was precisely observed by wide‐angle and small‐angle x‐ray scattering (WAXS and SAXS) using a strong synchrotron beam. In the TSC apparatus, the sample was crystallized in between a heater, controlled to 220°C, and a cooler, cooled by water to 25°C. We define the z‐axis parallel to the temperature gradient. A‐lamellae and B‐lamellae are also defined as those whose lamellar normal are perpendicular and parallel to the z‐axis, respectively. In a sample‐stop (SS) stage before the TSC, the original α‐phase lamellae became thicker, approaching to the melt‐solid boundary by annealing. The annealing process showed that the α‐phase B‐lamellae remained and the SAXS reflection was stronger on the meridian near the melt‐solid boundary in the SS stage. In the beginning of the TSC, the α‐phase B‐lamellae developed as a primary crystallization. During secondary crystallization under high supercooling, the SAXS cross pattern appeared showing that the α‐phase developed both A‐ and B‐lamellae. As the growth direction of A‐lamellae is parallel to the z‐axis, A‐lamellae grow faster than B‐lamellae. By the self‐epitaxial mechanism on the side surface of the A‐lamellae, the B‐lamellae grow on the base of the A‐lamellae. Following appearance of a spontaneous β‐nucleus, the β‐phase lamellae grew preferentially, excluding the α‐phase, and occupied the whole area of the sample. In this case also, A‐lamellae are advantageous to grow because of the growth direction parallel to the z‐axis. As a result, the SAXS β‐phase reflection appeared on the equator.  相似文献   

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