最新刊期
卷 14 ， 期 1 ， 1993
- 摘要：Quantum size effects and optical properties of PbS semiconductor ultrafine particles as well as the influence of the surrounding dielectric environment on their optical properties were investigated. It was found that the surface defects were effectively removed and the luminescence intensity of the particles was enhanced by surface modification. Experimental results are discussed with the tight-binding model.关键词：ultrafine particle;quantum size effect;surface modification107|53|2更新时间：2020-08-11
- 摘要：In comparison with tetratolylporphyrin (TTP) and phthalocyanine (Pc), the spectral properties of tetratolylporphyrin-phthalocyanine linked by covalence (TTP-O-Pc and TTP-O-(CH2)5-O-Pc) have been systematically investigated by measuring the absorption, emission, and excitation spectra.The interaction between donor (TTP) and acceptor (Pc) is dependent on the chain length of donor and acceptor. Our results show that there exists the energy transfer from TTP to Pc in TTP-O-Pc and TTP-O-(CH2)5-O-Pc. The relaxation time of charge measured is 18.5ps for TTP-O-Pc, and 82ps for TTP-O-(CH2)5-O-Pc by using a technique of laser frequency domain.关键词：energy transfer;charge relaxation;excited states110|69|0更新时间：2020-08-11
- 摘要：A technique of the degenerate four-wave mixing (DFWM) has been employed to study the nonlinear optical effects in binary molecules of TTP-O-Pc and TTP-O-(CH2)5-O-Pc. The third-order nonlinear susceptibility of X(3)in TTP-O-PC is increased by over two orders of magnitude compared with TTP and PC. With the increase of covalence length between TTP and PC from -O- to -O-(CH2)5-O-, X(3) of the latter is 3×10-9 esu that is 5 times of that of the former. The enhancement of the optical nonlinearity for binary molecules is attributed to the charge transfer. The inverse saturation absorption which is found in TTP and PC disappears in TTP-O-Pc and TTP-O(CH2)5-O-Pc owing to the ultra-fast transfer of intramolecular charge.109|60|1更新时间：2020-08-11
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RAMAN SCATTERING OF DOUBLE-LAYER DIELECTRIC SYSTEM——SURFACE PHONON MODES IN ZnSe/GLASS AND ZnSe/GaAs
摘要：The surface phonon modes of double-layer dielectric systems of ZnSe Glass and ZnSe/GaAs were observed experimently and calculated by means of boundary condition of polarization field. For ZnSe/Glass, the calculation shows that there are two surface phonon modes, whose positions lie between the TO and LO phonons of ZnSe, varying with the thickness of ZnSe film and the dielectric constant outside ZnSe film. The experimental results are in good agreement with those calculated. For ZnSe/GaAs, among the three calculated surface phonon modes, two modes were observed in experiment, whose Raman shifts are also accordant with the theoretical values. The third surface phonon mode predicted by the calculation did not appear in the measured spectrum , and we think that its position is too close to the TO pbonon of ZnSe to be detected.关键词：raman scattering;surface phonon mades;ZnSe/glass;ZnSe/GaAs100|81|0更新时间：2020-08-11 - 摘要：A series of La4(P2O7)3:Ce,Gd,Tb phosphors have been prepared by precipitation from aqueous solution and subsequent ignition.XRD measurements confirm that the products are pure phase La4(P2O7)3. Excitation and emission spectra,relative brightness and cerium luminescence lifetime of these phosphors have been obtained.It is shown that in the crystalline lattice of La4(P2O7)3,the spectra of Ce and Gd overlap with each other, rendering certain interaction to occur between them and hence bringing about some increase of brightness of (La0.64Ce0.3Gd0.06)4(P2O7)3 as compared to either (La0.7Ce0.3)4(P2O7)3 or(La0.94Gd0.06)4(P2O7)3.On the other hand,Ce effectively sensitizes Tb, enhancing the Tb emission considerably.However,the coexislance of Gd and Tb gives rise to competitive absorption and individual emission, rendering a slight decrease of the brightness of(La0.80Gd0.06Tb0.14)4(P2O7)3 as compared to that of singly doped(La0.86Tb0.14)4(P2O7)3.Consequently in the case of codoping of Ce, Gd,and Tb,the emission is also weakened.关键词：La4(P2O7)3：Ce;Gd;Tb phosphors;preparation;cerium luminescence lifetime91|64|2更新时间：2020-08-11
- 摘要：The absorption spectrum and the energy levels of Eu3+ of Na5Eu(WO4)4 crystal have been determined. The absorption edge lies at 290nm (4.3eV).The branch ratios of fluorescence lines of 5D0 to 7F1,2,3,4 are 0.041, 0.832, 0.006 and 0.121, respectively.The strongest fluorescence line(5D0 to 7F2(E)) is 617.2nm, the branch ratio of which is 0.637 and halfwidth is about 1.5nm. And the fluorescence of 5D1 and 5D2 to 7Fj is so weak at room temperature that they have not been observed in our experiment.According to Raman and infrared spectrum analyses, the energies of anti-symmetrical stretching vibration of WO42- in Na5Eu(WO4)4 crystal are very high.It will cause a strong non-radiation transition from 5D2 to 5D1 and then to 5D0. The lifetime experiment will support this further more.By using a YAG:Nd double frequency pulso laser (530nm, 6ns) to excite the Eu3+ ions from 7F0. to 5D1,the strong fluorescence was detected, which only belongs to 5D0→7Fj(j=1,2,3,4), but not to 5D1→7Fj. It means that an energy transfer from 5D1 to 5D0 is occured.The growing time of 5D0 to 7F2 (617.2nm) is 20ns. It indicates that the life time of 5D1 is about 20μs, which, is much less than about 1ms, the normal life time of 5D1 energy level (such as Eu3+ doped in Y2O3, Y2O2S and so on). It is shown that the nonradiation transition probability from 5D1 to 5D0 is very high. From this experiment, the decay time of 5D0 to 7F2 was determined to be 1.03ms. This decay time is in the same order of above materials doped with Eu3+ as an impurity. It is even shown that the concentration of Eu3+ is very high, but this material has no noticeable concentration quenching effect.Several parameters of Na5Eu(WO4)4 are determined. For example, transition probability of 5D0→7F2 is 724s-1, quantum efficiency of 5D0→ 7F2 is 0.90 and effective emission cross section of the 617.2nm main peak is l.5×10-20cm2, which is an order of magnitude larger than that in K5Eu(MoO4)4.关键词：Na5Eu(WO4)4;optical properties;single crystal92|56|1更新时间：2020-08-11
- 摘要：The phenomena of upconversion have attracted considerable interest of scientists in recent years and have been extensively studied in systems containing rare-earth ions. The upconversion pumping of rare-earth laser systems has been demonstrated.We have observed upconverted blue fluorescence in LiYF4:Nd3+ single crystal at room temperature and 77K under pulsed-pumping by a Rhodamine 580 dye laser. The pumping wavelength is 578.4nm. There are four regions in which emission is observed.They are near 357.8nm, 383.3nm, 414.9nm and 448.6nm at room temperature (near 357.6nm, 383.2 nm, 414.7nm and 456nm at 77K) which correspond to transitions from 4D3/2+4D5/2 manifolds to 4I9/2,4I11/2,4I13/2. and 4I15/2,respectively. That the peaks in the emission spectra at 77K do not appear in the corresponding emission spectra at room temperature and vice versa is dur to the change of ion distribution on energy levels by changing the temperature.The blue fluorescence intensity versus the square of pump intensity has been measured at room temperature. The linear relation shows that this upconversion process involves two photons.Decay cuive measurements of the excited 4D3/2 energy level fluorescence at room temperature and at 77K show that after excitation the fluorescence increases first,reaches maximum,and then decay.This shows that energy transfer is involved in upconversion process at room temperature and at 77K.At room temperature, most of the absorption peaks in the absorption spectrum appear in the excitation spectrum. This indicates that two-step excitation is involved in upconversion process.关键词：two-step excitation;energy transfer upconverison;up-converted fluorescence96|55|0更新时间：2020-08-11
- 摘要：The Rh·6G dye laser was pumped by a home-made Q-YAG laser. The tunable dye laser beam (562-598nm) was used to generate the sum frequency with the double-frequency beam of YAG laser in β-BaB2O4 (BBO) crystal. The continuously tunable range of 271-281.5nm was obtained. The output energies of sum frequency are larger than 200μJ. The largest conversion efficiency is about 5%. The tuning curves of sum frequency were calculated by BBO Sallmeier equations of C. Chen and K.Kato. The angular differential of phase matching angle of both theoretical tuning curves is about one degree. There are deflections in varying degree between the experimental curve and the theoretical calculated curves. But, the theoretical curve calculated by BBO Sellmeier equention of Kato is very close to the experimental curve. We have discussed the influence of BBO crystal length on the output energy, and explained the cause generating the influence.关键词：β-BaB2O4 crystal;sum frequency generation124|65|0更新时间：2020-08-11
- 摘要：RE glass is a kind of potentiaily valuable luminescent material.More than forty types of various glass doped with various concentration of Ce3+, Gd3+ Sb3+ ions and co-doped with Ce3++Gd3+ ions were investigated. The influence of glass compositions and concentrations of Sm3+ ion on the luminescence of Sm3+ ions and the sensitization effect of Ce3+ Gd3+, Sb3+ and Ce3++Gd3+ on Sm3+ ion were also studied.The results indicate that the luminescence of Sm3+ depends not only on the composition of qlass but also on the concentration of Sm3+ ion. The concentration quenching occurs at 2wt% of Sm3+ in borate glass. However,concentration guenching was not found in silicate glass and phosphate glass. It is possible that their critical quenching concentrations are larger than 3wt%. The ions of Ce3+, Gd3+, Sb3+ can sensitize the Sm3+ luminescence. When sensitized by Ce3+, Gd3+, Sb3+ and Ce3++ Gd3+, the emission intensity of Sm3+ increased by a factor of 1.5, 2.0, 3.7, and 2.6, respectively.关键词：Samarium ion;luminescence;stibium ion;cerium ion;Gadolinium ion;sensitization;glass102|60|1更新时间：2020-08-11
- 摘要：In this paper an up-conversion luminescence phenomenon at room temperature in HoP5O145G4(3G,5G)5, 5F3,5S2→5I8 and 5G4→5I7 transitions were observed. The dependence of the emission signal on the laser energy shows that all of them belong to a two-photon process. The excitation spectra for all of up-conversion emissions have a same peak possition as that of 5I8→5F5 absorption line and a very similar shape. Its value is equal to the square of this absorption shape. All of these indicate that they come from the same origin, the pump photons are absorpted by more than one ion, and energy transfer between ions via the interaction should be responsible for this up-conversion.Most likely, the homo-or hetero-excited pair of nearest neighbour Ho3+ ions, which result from the subsequent resonant energy transfer and nonradiative relaxation, exchange their energy to add to one .ion and bring about the population of above mentioned higher excited states. The time-resolved experiments further support our inference. Compaied to the fluorescence excited by 355nm laser, the anti-stokes line of (5G, 3H)5→5I8 dose not show up, but the relative intensity of 5F3→5I8 emission is about twice enhenced, which shows that among so many possible up-conversion channels this one seems to be the strongest.关键词：up-conversion;HoP5O14 noncrystalline97|57|0更新时间：2020-08-11
- 摘要：In basic medium, acetone can react with CIO- and H2O2 to produce chemiluminescence (CL) emission. The halide ions were found to sensitize the acetone CL reaction. The mechanism of the halide sensitization effect has been briefly discussed. Based on this effect, a novel CL method for the determination of iodide ion was proposed. The experimental results illustrate that the detection limit is 2.0×10-11g/ml I-, and the linear range is 4.0×l0-1g/ml to 3.0×10-7g/ml. The effect of some foreign ions was also studied.关键词：acetone;chemiluminescence;halide effect96|70|0更新时间：2020-08-11
- 摘要：A new sensitized fluorescence phenomenon was observed by adding some of metal ions to europium, samarium-dibenzoylmethane-cetylpyridium bromide(Eu, Sm-DBM-CPB)or europium, samarium-lhenoyltrifluoroacetone-1, 10-phenanthroline-Triton X-100 (Eu, Sm-TTA-Phen-TX-100) systems, which is named as a synergistic luminescence effect. The synergistic luminescence effect and its luminescent mechanism were studied using laser--induced fluorimetry.The influence of the chemical properties of rare earth ions on the synergistic luminescence effects of above systems is reported. In general, the synergistic luminescence effect is enhanced with the increase of ionic radius of synergistic ions. The systems exhibit similar fluorescence characteristics in the presence of different synergistic ions.From the experimental results, a mechanism of synergistic luminescence is proposed. The following factors affect the synergistic luminescence.1. Synergistic ions do not form new chelates with luminescent ion chelates. The solid solution is formed between luminescent ion chelates and synergistic ion chelates.2. Synergistic luminescence effect is influnced by the structure and symmetry of the chelates of luminescent ion and synergistic ion. 3. All the synergistic ions which have enhanced effect, except terbium, dysprosium and ytterbium, possess 8 stable outer electronic orbit. The synergistic luminescence effects of terbium,dysprosium and ytterbium ions can be explained by the valence fluctuation between the synergistic ions and ligands.The excitation energy transfer plays an important part in the energy transfer of synergistic luminescence effect.The proposed method can be used for determination of trace amounts of europium and samarium. Results are satisfactory for the determination of trace europium and samarium in highly pure rare earth oxides and synthetic samples without pre-separation.关键词：synergistic luminescence effect;rare earth;fluorimetry146|89|2更新时间：2020-08-11
- 摘要：In the early 1970's, Ibach made the low energy electron diffracting experimentation on the surface of semiconductor [ZnO etc.. The surface polarop in the crystals was of considerable interest. Evans, Mills and Sak studied theoretically the surface polaron in polar crystals for the first time. Evans et al. investigated the effect of bulk LOphonon on the surface polaron. Gu et al. discussed ideal surface polaron and the weak and intermediate coupling polaron in semi-infinite polar crystal. There is a weak coupling between electrons and BO SA phonons but a strong coupling between electrons and SO phonons for many kinds of polar semiconductors. For αs>2.5, it belongs to the strong coupling.In this paper, the properties of the surface electrons in polar semiconductor, which is coupled both with SO BO and SA phonons, are studied. The effective Hamiltonian and the renormalization masses of the surface electrons are derived by using a linear-combination-operator and Lagrange multiplier method.The Hamiltonian of the electron-phonon system can be written as(la). We introduce the creation and annihilation operator B and B by (3) and carry out the unitary transformation U1 and U2. The ground state wave function of the system is φ=φ(p)|0>. In the unitary transformation, U1 with A1=0, A2=A3=1 corresponds to the weak coupling between electrons and BO SA phonons and the strong coupling between electrons and SO phonons.We now consider two limit cases.1. The electron is near the surface, i.e. z<<uL-1. In this case, we have (20) and (21).2. The electron goes very deep into the bulk, i.e. z>>uL-1 In this case, we get (23) and (24).The effective Hamiltonian, the self-trapping energy,the image potential and the rencrmalization masses cf the surface electrons in the two limit cases are discussed.关键词：polar semiconductor;surface electrons;effective bamiltonian120|83|1更新时间：2020-08-11
- 摘要：BaFX(Cl,Br) possesses the tetragonal structure of PbFCI. Its space group is P4/nmm. BaFX(Cl,Br) activated with divalent Eu2+ are used as X-ray phosphors for medical imaging. The photostimulated luminescence (PSL) process of BaFX (Cl,Br): Eu2+ irradiated by X-ray connects with the F-H center pair. The defects play an important part in PSL.Under 800℃, undoped BaFCl phosphors were prepared in N2 gas atmosphere. After the samples of BaFCl were irradiated by X-ray at 80K, we observed 310nm and 380nm emission peaks under 580nm photostimu-lation in the temperature range of 80K to 273K. The intensities of two peaks depend on the temperature as shown in Fig.1.At low temperature, electrons and self-trapped holes are created in BaFCl under X-ray exposure. Their recombination produces self-trapped excitons, and the excitons annihilate nonradiatively to create F-H center pairs. The process is shown in the Fig.2. Fncenter is regarded as an electron trapped in a vacancy of the halogen ion while H center is regarded as an X2- molecule occupying an X-ion site (X- is the halogen ion). When the sample is pholostimulated by 580nm light (F center optical absorption band) the electron of F center runs away and is trapped by the H center. Then it produces the self-trapped exciton with the STE (self-trapped exciton) recombinative luminescence. Fig.3 shows the above process.Yute et al. reported the absorption peaks of F center and H (Cl2-) center from the absorptive spectrum of BaFCl single crystal at 77K. Stimulating light with the wavelength of F center absorption band irradiates the sample of BaFCl after X-ray exposure. We have measured the self-trapped exciton's luminescence of the F-H (Cl2-) center pair at 380nm. In analogy to the intrinsic luminescence of BaF2 crystal, the 310nm peak is from the self-trapped exciton's luminescence of the F-H (F2-) center pair.The intensity of the two peaks deperds OD the temperature. 310nm emission intensity changes significantly between 80K and 170K. The self-trapped exciton produced by F-H (F2-) center pair is not oriented with its fluorine-fluorine axis in the a-b plane, in fact, may be oriented with the fluorine-fluorine axis at an angle of less than 90° with respect to C axis. This reorientation may require an activation energy which is not available at lower temperature and therefore the 310rm emission would be reduced in intensity below 170K.As stated above, 380nm peak is from the F-H (Cl2-) center pair and 310nm peak is from the F-H (F2-) center pair.关键词：X-ray exposure;F-H center pair;self-trapped excitons94|87|1更新时间：2020-08-11
- 摘要：High brightness eramel electroluminescent (AC-EL) lamps have been fabricated by use of an improved enamel dielectric material and a special firing process. The keys to fabricate high brightness enamel EL lamps are the large dielectric constant and improved composition of the enamel medium resulting in the decrease of firing temperature of emissive layer from 800℃ reported to 680℃ and the addition of a certain amount of ZnO and activator. The brightness of the enamel EL lamps is 48cd/m2, 92cd/m2 and 10.6cd/m2 under the excitation of 400Hz -175V,1kHz-175V and 50Hz-220V, respectively, reaching the advenced level in China.关键词：enamel;AC-EL lamp96|59|0更新时间：2020-08-11
- 摘要：The porous silicon (PS) was prepared by means of irradiation with He-Ne laser beam for the first time. Polished n-type(100) silicon wafers with resistivity 2-3Ω·cm were used as substrate. The silicon wafers were immersed in HF-H2O solution without current and irradiated with He-Ne laser beam. The position of PS formation is freely selected and the size of PS can be controlled by this technique.The surface morphology differs from that of anodized PS. It presents a distinct interference fringes. PL spectrum shape is similar to that of anodized PS. The samples excited by UV light or 488nm line from Ar ion laser at room temperature show intence red or orarge colour luminescence. It is found that the peak shifts to shorter wavelength and the PL intensity is obviously increased as the irradiating time is increased. Our experimental results show that this technique is not fit for p-type silicon wafers.108|107|0更新时间：2020-08-11
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