共查询到20条相似文献,搜索用时 31 毫秒
1.
Comparison of luminescence properties between electron-excited and uv-excited yttrium gallium garnet: Tb phosphors is reported. Although the thermoluminescence and phosphorescence in both cases are quite alike once traps are filled, an apparent difference in the behavior of trap filling has been observed. Small addition of V2O3 to these phosphors revealed a unique effect on luminescence properties either with the electron excitation or with the uv excitation. 相似文献
2.
Charles H. Warren 《Journal of Molecular Spectroscopy》1980,83(2):451-461
Discrete visible fluorescence has been observed from excitation of the fluorosulfate radical with argon-ion laser excitation which falls within its visible electronic absorption spectrum. Ground-state fundamentals of the radical have been determined which are in agreement with those determined from the analysis of the hot bands in the electronic absorption spectrum. The analysis of the fluorescence spectrum is consistent with the molecule possessing C3r symmetry in the ground electronic state. 相似文献
3.
《Infrared physics》1985,25(4):595-598
Photogenerated currents at 77 K, when the Semitransparent gate of an Hg1−xCdxTe(x = 0.205) n-channel MISFET is illuminated with IR radiation of varying intensities, have been evaluated theoretically. Two different processes of excitation are considered, namely, electron-hole pair excitation across the bandgap in the depletion layer of the field-induced junction and excitation of carriers to the conduction band from surface states lying near the middle of the bandgap. The photocurrent, in this case, is primarily due to the latter process. For the sake of comparison, the drain-source current without illumination has also been calculated as a function of the gate voltage. 相似文献
4.
Prototype devices based on black silicon have been fabricated by microstructuring 250 μm thick multicrystalline n doped silicon wafers using femtosecond pulsed laser in ambient gas of SF6 to measure its photovoltaic properties. The enhanced optical absorption of black silicon extends across the visible region and all the black silicons prepared in this work exhibit enhanced optical absorption close to 90% from 300 nm to 800 nm. The highest open-circuit voltage (Voc) and short-circuit current (Isc) under the illumination of He–Ne continuous laser at 632.8 nm were measured to be 53.3 mV and 0.11 mA, respectively at a maximum power conversion efficiency of 1.44%. Upon excitation with He–Ne continuous laser at 632.8 nm, external quantum efficiency (EQE) of black silicon as high as 112.9% has also been observed. Development of black silicon for photovoltaic purposes could open up a new perspective in achieving high efficient silicon-based solar cell by means of the enhanced optical absorption in the visible region. The current–voltage characteristic and photo responsivity of these prototype devices fabricated with microstructured silicon were also investigated. 相似文献
5.
M. V. Bogatyrenko S. I. Bredikhin 《Journal of Experimental and Theoretical Physics》1997,85(2):381-385
A new effect of illumination on ionic conductivity and activation energy of migration of mobile Ag+ cations in RbAg4I5 superionic crystals has been detected and studied. Reversible changes in the ionic conductivity due to illumination of superionic
crystals are caused by reversible changes in the structure of electronic centers caused by elastic strain around these centers.
The effect of elastic deformation on the process of ionic transport and activation energy for diffusion of mobile silver cations
has been studied. Photostimulated recovery of the ionic conductivity after its change due to preliminary illumination of a
RbAg4I5 superionic crystal with light of wavelength λ≃430 nm has been detected. This recovery of the ionic conductivity is due to excitation of centers in complexes generated
by previous illumination of tested samples.
Zh. éksp. Teor. Fiz. 112, 698–706 (August 1997) 相似文献
6.
I. N. Knyazev Yu. A. Kudriavtzev N. P. Kuzmina V. S. Letokhov A. A. Sarkisian 《Applied Physics A: Materials Science & Processing》1978,17(4):427-429
A new approach to laser isotope separation is considered. It is based on collisionless multiple photon ir laser excitation
and subsequent uv laser dissociation of vibrationally excited molecules. TEA CO2 and excimer XeF, XeCl lasers are used for ir excitation and uv dissociation, respectively. The products of photolysis (C2F6) are enriched with12C. 相似文献
7.
J. K. Chen C. Y. R. Wu C. C. Kim D. L. Judge 《Applied physics. B, Lasers and optics》1984,33(3):155-160
We report the observation of coherent uv emission at 330.2±0.5 nm when sodium vapor in a heatpipe is irradiated with a pulsed visible dye laser with output wavelength in the 570–595 nm region. It is found that intense uv emission can be produced from Na atoms as well as from Na2 molecules. The excitation functions and their dependence on vapor density and laser power density are presented and the mechanisms for producing the emission are discussed.On leave from the Department of Physics, Fujian Normal University, Fuzhou, Fujian, People's Republic of China 相似文献
8.
Luminescence spectra and excitation spectra in 150-420 nm spectral region have been recorded at room temperature for polycrystalline sample of (0.5%)Eu3+:CsGd2F7. The relatively intense emission has been observed from 5D3, 5D2 and 5D1 levels. Emission and excitation spectra prove that the excitation energy is efficiently transferred from the 6GJ and 6IJ levels of Gd3+ ions to Eu3+ ions. The visible quantum cutting via downconversion has been detected, with efficiency of the cross-relaxation step of ∼50%. 相似文献
9.
G. Stryganyuk G. Zimmerer N. Shiran V. Nesterkina K. Shimamura F. Jing A. Voloshinovskii 《Journal of luminescence》2008,128(12):1937-1941
Spectral-kinetic study of Pr3+ luminescence has been performed for LiLuF4:Pr(0.1 mol%) single crystal upon the excitation within 5-12 eV range at T=8 K. The fine-structure of Pr3+ 4f 2→4f 5d excitation spectra is shown for LiLuF4:Pr(0.1 mol%) to be affected by the efficient absorption transitions of Pr3+ ions into 4f 5d involving 4f 1 core in the ground state. Favourable conditions have been revealed in LiLuF4:Pr(0.1 mol%) for the transformation of UV-VUV excitation quanta into the visible range. Lightly doped LiLuF4:Pr crystals are considered as the promising luminescent materials possessing the efficient Pr3+3P0 visible emission upon UV-VUV excitation. The mechanism of energy transfer between Lu3+ host ion and Pr3+ impurity is discussed. 相似文献
10.
Mu Yao Guo Fangzhou Liu Yu Hang Leung Alan Man Ching Ng Aleksandra B. Djurišić Wai Kin Chan 《Current Applied Physics》2013,13(7):1280-1287
We investigated the influence of the crystal structure of TiO2 and the use of different TiO2 precursors on the properties and photocatalytic activity of carbon nanotube (CNTs)–titania composites. We found that the crystal structure and properties of starting TiO2 nanomaterial significantly affected the effect of CNTs incorporation on the photocatalytic activity under simulated solar and visible light illumination (simulated solar illumination with UV-blocking filter). In case of significant photocatalytic activity under visible light illumination (anatase TiO2), likely due to the presence of native defects, composites exhibited lower activity under visible illumination only, but higher activity under simulated solar illumination. The opposite trends were observed for P25 (anatase + rutile) and rutile TiO2, where incorporation of CNTs resulted in a significant increase of photocatalytic activity under visible illumination. Thus, control over crystal structure and native defects is essential for the development of efficient visible light activated photocatalysts. 相似文献
11.
A.V. Nurmikko 《Optics Communications》1976,18(4):522-524
Near band-edge illumination of Hg1?xCdxTe (x ≈ 0.2) by short bursts of CO2 laser radiation has been shown to lead to highly nonlinear absorption and saturation. For sufficiently high infrared intensities the transmission through an absorber is enhanced more than three orders of magnitude. The effect should be useful in temporal shaping of high intensity CO2 laser pulses. 相似文献
12.
H. Huhtinen R. Laiho L.S. Vlasenko M.P. Vlasenko V. Zakhvalinskii J. Leiro S. Mattila F. Sutara M. Vondracek 《Journal of magnetism and magnetic materials》2008
Light-induced changes of the hysteresis loops of magnetization and microwave absorption are investigated in low-doped La1−xCaxMnO3 (x<0.2) thin films. The width of the hysteresis loops decreases clearly under illumination with visible or near-infrared light at temperatures below 50 K. The microwave conductivity has a minimum value at magnetic fields corresponding to the magnetization reversal and is shifted towards weaker fields under illumination. These effects show complex nonexponential time evolution and dependence on strength of the magnetic field. The results can be explained by assuming that small ferromagnetic metallic regions exist within the insulating ferromagnetic phase of the sample, and that these regions are expanded by optically induced charge transfer between Jahn–Teller split eg states of neighboring Mn3+ ions. Decrease of the Mn3+ XPS core level spectrum is observed in the samples under illumination with a HeNe laser. 相似文献
13.
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
14.
Photoemission from a semiconductor having a negative electron affinity under nonuniform illumination is investigated theoretically for stationary and pulsed excitation regimes. The maximum emission current is shown to grow exponentially with increasing ratio of the negative electron affinity Δ0 to a characteristic tunneling energy E 0, and the excitation intensity I opt corresponding to the maximum current has been determined. Excitation nonuniformity results in a weakening of the dependence of the emission current on illumination intensity near the current maximum. The quantum efficiency recovery time measured in a two-pulse excitation mode depends weakly on the illumination intensity and on its nonuniformity over the illuminated spot and is close to the relaxation time of low photovoltages. 相似文献
15.
We have recorded the 5350 Å (30, 0) band of the iodine spectrum with high resolution by means of Fourier transform spectroscopy. The rotational lines in the P and R branches were measured to J = 165 with reference to uranium standards emitted by a hollow cathode. The differences between the two sets of measurements were less than 0.001 cm?1, and the standard deviation between the observed wavenumbers and those calculated with the spectroscopic constants Bv, Dv, and Hv is 0.0007 cm?1. The precision reached is an order of magnitude greater than in previously published data, and the constants Hv of the iodine absorption spectrum have been determined for the first time. This work shows that the use of Fourier transform spectroscopy is particularly powerful for molecular absorption studies in the visible region where, although the multiplex gain is lost, the throughput gain remains, and this enables the performance to approach that achieved in the infrared. This method can be expected to open up not only significant new spectroscopic experiments, but it also allows a complete high-precision remeasurement of the existing molecular spectra in the visible and uv (electronic rotational-vibrational transitions). 相似文献
16.
A new kind of melting phenomenon which is not based on thermal excitation has been observed. X-ray absorption spectroscopy (XAS) experiments under optical pumping provide a “snap-shot” information on the local structure under excitation. We have studied the local structure of chalcogenide glasses such as vitrious selenium and As2Se3 under optical excitation and confirmed the local melting phenomenon under light illumination at low temperature. The photo-induced nonthermal melting (PNM) in chalcogenide glasses is interpreted as the result of pairing of excited lone pair electrons during the illumination. Trapped states in this photo-assisted metastable phase result in a local structural disorder which is partially quenched at room temperature. The increased short-range disorder causing Coulomb repulsion is the origin of red shift of the absorption coefficient known as the photodarkening effect. We found that the bond alternation of chalcogens occurs during the photo-excitation. 相似文献
17.
C. Radzewicz P. Kowalczyk J. Krasiński 《Zeitschrift für Physik A Hadrons and Nuclei》1983,314(3):293-296
A dense sodium vapour (T=450°C) has been illuminated with a laser light tuned across the whole visible region. For any laser wavelength the diffuse violet band of Na2 molecule (peaking at 436.5 nm) has been found in fluorescence spectrum. Several mechanisms are proposed for excitation of the diffuse band, including collisional energy transfer and ionization-recombination processes. New observations of a spectral shape of the diffuse band are reported. 相似文献
18.
New organic/inorganic hybrid material containing a ferrimagnetic cyano-bridged binuclear complex, [Gd(DMF)4(H2O)3Cr(CN)6]·H2O (DMF=N,N′-dimethylformamide), and photochromic azobenzene in poly(methylmethacrylate) (PMMA) cast films has been prepared. We characterized magnetic properties of bulk [Gd(DMF)4(H2O)3Cr(CN)6]·H2O and confirmed that it was not changed by light illumination at all. For the first time, we could detect reversible changes of both DC and in-phase AC susceptibility for the hybrid materials accompanying with cis–trans photoisomerization of azobenzene after UV and visible light illumination for 3 min at 3 K. We also discuss the kind of detectable magnetic changes (e.g. DC, in-phase AC, and both DC and in-phase AC) and the nature of some photo-magnetic functional hybrid materials (cis–trans photoisomerization and increase/decrease of magnetization) known to estimate their mechanism and interactions. 相似文献
19.
Intense infrared stimulated lines at wavelengths around 2.5 μm have been observed upon excitation of Na2 by uv radiation from a frequency-doubled narrow-band dye laser. Frequencies of these IR lines have been measured when the pump laser was tuned to C1Πu ← X1Σg+ assigned transitions in the wavelength range 331–334 nm. High-resolution spectroscopy measurements of the involved rovibrational levels of both C1Πu and 31Σg+ electronic states allow the unambiguous assignment of these IR laser lines to C1Πu → 31Σg+ transitions. 相似文献