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1.
Emission from the high lying excited states, energy transfer, and upconversion processes are investigated in YAlO3:Ho3+. Selectively excited emission spectra in the range from 300 to 800 nm starting from the 3D3, 3G5, 5F3, 5S2 and 5F5 multiplets were measured at 15 K. This, together with the detailed absorption and excitation measurements at 15 K allowed determination of the Stark energy levels of Ho3+ ions in YAlO3 up to UV energies. The 5S2 fluorescence decays were recorded as a function of temperature and Ho3+ concentration in order to investigate the process of quenching of fluorescence due to cross relaxation among two ions. Conversion of red and infrared laser radiation to green 5S2 and blue 5F3 emission is reported. Under pulsed resonant excitation of the 5F5 or 5I5 levels the upconversion was found to be due to energy transfer process between two excited ions. The photon avalanche effect was observed under cw excitation around 585 nm.  相似文献   

2.
Fullerene hydrides of C60H18, C60H36 and C70H36 are studied by using IR, 1H and 13C NMR, X-ray photoelectron and electron energy loss spectroscopies, and magnetochemistry. The comparison of IR and solid state 1H and 13C NMR data for C60H36 with the theoretical ones allows the suggestion that fullerene hydride has a T symmetric structure and contains 4 isolated benzenoid rings located at tetrahedral positions on the surface of a closed skeleton of the molecule. The EELS revealed that the transition from fullerene to the hydride is accompanied by the decrease of the density of valence electrons. Magnetization measurements showed C60H36 to be a ferromagnet. The hydrogenated fullerenes were prepared by transfer hydrogenation procedures involving 9,10-dihydroanthracene. The compositions of the hydrides are determined by field desorption mass-spectral analysis.  相似文献   

3.
The binary diffusion coefficient DAB of subliming C60 in He, N2 and Ar gas has been determined at a gas pressure between 5 and 10 kPa. It resulted DAB/(cm2/s)=Do(Po/Pt(T/To)n as a function of the total pressure Pt of the vapor phase and temperature T. At To=273 K and Po=1.0133×105 Pa, the values Do = (0.059±0.004) cm2/s, (0.011±0.003) cm2/s, (0.012±0.007) cm2/s, n = 1.77±0.06, 2.02±0.18, 1.77±0.37 were obtained for He, N2, Ar and (830-1000) K, (800-1020) K, (875-1095) K, respectively. Only 40 wt% of the initial C60 material yielded reliable DAB where the vapor pressure of C60 followed log10(P/Pa) = -(8976±60)/T/K+(11.05±0.07) for T between 640 and 1055 K.  相似文献   

4.
Extensive NMR experiments have been performed both on the 13C and the alkali NMR in AnC60. In the superconducting A3C60. evidences for uniaxial molecular rotations of the C60 and for a low T structural anomaly will be given. The linear chain structure of A1C60 is revealed by Magic Angle Spinning NMR, while its magnetic properties are studied by 13C and 87Rb wideband NMR.  相似文献   

5.
The synthesis of radiolabeled C60/C70 for potential biochemical tracer studies was carried out. Vaporization under plasma are conditions (~3000C) of graphite rods impregnated with the 14C labeled steroid progesterone generates the expected C60/C70 mixture. Isolation and characterization of the 14C-C60 is reported. Interestingly, the C70 had more radioactivity than the C60.  相似文献   

6.
A new homemade are fullerene generator used in this experiment is reported. The comparation of yields of fullerenes (C60/C70 mixture) was studied by different power supplies (AC and DC), different gaps of two graphite rods and different He pressure between 0.4×104- 2.8×104 Pa. In our experiment, the highest yield up to 13% was achieved, when DC discharge was used and the optimum He pressure was near 0.8×104 - 1.6×104 Pa.

The mixed fullerene was analyzed by electron impact masa spectnun (EIMS). The relative amount af C60 to C70 was 4.2 to 1. After column chromatography aeperation with hexane on alumina, 99.9% Cso was obtained. FTIR and 1aC-NMR epectrum were ueed to characterize the pure C60 samples.  相似文献   

7.
The dynamic Young’s modulus, E, of amorphous (a-) Zr60Cu30Al10 (numbers indicate at.%) alloy was measured as a function of frequency, f, with a strain amplitude, t, of 10−6, E(10−6,f), and also as a function of t for f near 102 Hz, E(t,102 Hz), by means of the vibrating reed methods. The elasticity study under the passing of electric current (PEC) was carried out too. E(10−6,f) is lower than E0 for f between 10 and 104 Hz showing local minima near 5×10, 5×102 and 5×103 Hz, which are indicative of the resonant collective motion of many atoms, where E0 is the static Young’s modulus. E(t,102 Hz) increases showing saturation with increasing t. Qualitatively, the outlines of E(10−6,f) and E(t,102 Hz) observed for a-Zr60Cu30Al10 are similar to those reported for various a-alloys. Quantitatively, a change in E(t,102 Hz) for a-Zr60Cu30Al10 is smallest among that reported for various a-alloys, presumably reflecting that the crystallization volume, (ΔV/V)x, is smallest for a-Zr60Cu30Al10. The effective charge number, Z*, estimated from the change in E(10−6,102 Hz) due to PEC is 3.0×105, which is comparable with Z* reported for various a-alloys. We surmise that the number of atoms in the collective motions excited near 102 Hz is similar among various a-alloys. The E(10−6,f) data suggest that the spatial sizes of the density fluctuations may show a distribution.  相似文献   

8.
The increase with increasing temperature of KIc, measured with 2CT and 1'CT specimens, from about 103N mm at 77 K to about 2.103 N mm at about 170 K is attributed to the increasing proportion of dimple to cleavage fracture as revealed by scanning electron microscope investigation.

The specimens were prestrained to different partial scale yielding states by the same kind of loading, performed at 298 K, as in the later KIctests, performed at 77 K. After pretension KIc = K*Ic is increased by a maximum amount of about half of the value K0Icof nonprestrained specimens, after precompression it is reduced by the same amount if this value is evaluated from the load at which a pop-in occurs. The value KIc = K**Ic for the final fracture lies between K*Ic and K0Ic. These results are interpretated in terms of the residual stress states due to prestraining.  相似文献   


9.
Photochemical reactions of M(CO)6 (M = W, Mo) with C60 in solution yield η:2-complexes of M(CO)5 with C60. The complexes have been characterised by IR, UV/VIS, NMR and DSC. They do not show any orientational ordering down to 12 K and all the infrared bandwidths remain the same down to this temperature. The complexes can be decomposed thermally or photochemically yielding metal fullerides, which show characteristic reduction in peak width in the variable temperature IR spectra due to orientational ordering. Transitions are manifested in calorimetric studies also. Metal → C60 charge-transfer is observed in IR and XPS. A high temperature IR study of the C60-W(CO)5 complex reveals sequential elimination of the carbonyls yielding MC60. The study shows that carbonyl complexes can be used as precursors to make transition metal fullerides.  相似文献   

10.
Results of XRD, optical absorption spectra, photoconductivity, photovoltaic effect and photoluminescence are reported for (Cd0.95–Pb0.05)S:CdCl2,Gd films prepared by chemical deposition technique at 60 °C and room temperature (RT). The XRD studies show prominent diffraction lines of CdS and PbS. Optical absorption spectra show direct bandgap nature with decreasing value due to addition of PbS. The saturated photocurrent (Ipc) to dark current (Idc) ratios 107 are found in films prepared at 60 °C and 104 in films prepared at RT. Photoluminescence is found to be brighter in films prepared at RT. Photovoltaic efficiency 5% has been observed in such films.  相似文献   

11.
Six new organic cations (Triphenylmethane dye, Hemicyanine dyes, calix[4]arene derivative) buckminsterfulleride salts were prepared by metathetical reaction. the products were characterized by UV-NIR, ESI-MS, ESR and FT-IR. the ESR spectra show a typical C60 anion radical signal and dependence on countercations and temperature, the linewidth has an abrupt increasing at about the THF melting point and the ESR signal diminishes gradually when the temperature below 170K. the possible explanation is that the THF crystallization results in exclusion of solute from the lattice and leads to C60 anion aggregation, which promotes line broadening and diamagnetic dimer of (C60)2 2- forming.  相似文献   

12.
N-type doping of the C60 films deposited on Si substrates has been achieved by 80 keV P+-ion implantation with doses of 2×1014 cm-2 at room temperature. The heterostructures composed of the n-type doped C60 films and n- or p-type Si(111), Si(100) substrates are studied in view of semiconductor heterojunctions. The rectification and other electrical characteristics of the P+-ion implanted n-C60/n-(p-)Si heterostructures are disclosed by the current-voltage (I-V) measurements at room temperature. The n-C60/p-Si heterostructures show stronger rectification than n-C60/n-Si heterostructures and Si(111) substrates are found to be more suitable for forming n-C60/Si heterostructures than Si(100) substrates.  相似文献   

13.
用高温熔融法制备了Bi、Tm、Bi/Tm掺杂TiO2-BaO-SiO2-Ga2O3玻璃系统。在808 nm激光激发下, 与Tm单掺杂玻璃相比, Bi/Tm共掺玻璃中Tm3+3H43F4跃迁荧光(~1485 nm)得到了显著的增强, 而Tm3+3F43H6跃迁荧光(~1810 nm)减弱。在980 nm激光激发下, Tm单掺玻璃中没有观察到Tm离子的特征发光, 而在Bi/Tm共掺玻璃中观察到Tm3+3F43H6跃迁荧光(~1810 nm)。这是由于在808和980 nm激光二极管(LD)各自激发下, Bi/Tm共掺玻璃中活性Bi离子的近红外发光能量传递给Tm3+, 分别产生3F43H43H63H5跃迁所致。采用Inokuti-Hirayama模型, 分析了该玻璃体系中Bi→Tm的能量传递机理。结果表明, Bi→Tm的能量传递属于电偶极–偶极相互作用。  相似文献   

14.
The n,γ-reaction of metallofullerenes of Tb, Sm and Sc3N@C80 is studied. Unusually high compared to trivalent lanthanofullerenes retention yield is observed for 153Sm@C2n. The recoil implosion yield of 177Lu atom in molecularly tight mixture of Lu diphthalocyanine and C60 is measured. It is shown that possibly unfavorable geometry of target/projectile system can not explain low implosion yields observed so far. Possible role of chemical properties of recoil atom at hot atom-cage interaction and mechanisms of energy dissipation are discussed.  相似文献   

15.
Efficient electron-transfer reactions from three kind of tetraselenafulvalenes (TSeF's) to photoexcited triplet state of C60 or C70 in polar solvents have been confirmed by transient absorption spectroscopy observing the decay of 3C60*/3C70* and rise of C60-•/C70-•. Growth of single crystal seems to be stimulated by laser irradiation of the solution containing C60 and bis(ethylenedithio)tetraselena-fulvalene (BEDT-TSeF), in which C60-• was effectively formed.  相似文献   

16.
针对频率标准用超导腔的设计,通过理论分析及编程计算得到了影响微波腔指标的参数,并对不同温度下微波腔的品质因数(Q值)进行计算得到了温度变化曲线,通过此曲线可以确定达到指标所需要的温度。所设计的微波腔参数为:工作模式为TM010模式,直径D为60mm,高度l为50mm,频率为4.4GHz,Q值在液氦温度4.2K时达到3.9×107,在减压降温到2K时达到1.9×109,实验结果与计算结果吻合。  相似文献   

17.
The quantitative diagnostics of carbon arc during the process of carbon nanostructure formation is presented. Temperature within 3500-5500 K and concentration within 2*1015 - 2*1016 cm-2 of C2(a 3IIu, v=0) were determined upon input power and plasma coordinates at arc gap 0.5 ± 0.2 mm favoring the process yield. The total carbon vapor pressure in the discharge zone was estimated as equal to 30 kPa.  相似文献   

18.
From the products of reactions of [60]fullerene with either K2PtF6 at 470 °C or AgF at 520 °C, we have isolated C60(CF3)2, the simplest trifluoromethylfullerene, which gives a single 19F NMR line at -69.5 ppm. The HPLC retention time is less than that of C60F2 confirming the trend observed for other fluoro- vs. trifluoromethylfullerenes namely that the latter elute more rapidly. Other trifluoromethyl- containing species, C60(CF3)4O, C60F5CF3, C60(CF3)4H2, C60(CF3)6H2, and C60(CF3H)3 were detected in the product mixture.  相似文献   

19.
采用简单的液相法在室温下制备了均匀球形的Ag-SiO2-CeF3:Tb3+核-壳结构纳米复合发光粒子,并对其结构和性能进行了表征。测试结果表明:Ag-SiO2表面包覆上了结晶良好的六方晶系的CeF3:Tb3+。Ag-SiO2-CeF3:Tb3+纳米复合粒子为球形,尺寸约为45~60 nm,该纳米复合粒子与CeF3:Tb3+一样具有良好的特征绿光发射,均以544 nm附近的Tb3+5D47F5跃迁为最强发射峰,内核贵金属Ag纳米粒子对CeF3:Tb3+发光起到了一定的猝灭作用。Ag-SiO2-CeF3:Tb3+复合材料在生物检测、疾病治疗方面具有潜在的应用。  相似文献   

20.
Thermoluminescence (TL) of gadolinium oxysulfide activated with terbium (Gd2O2S:Tb) is investigated. The glow curves of Gd2O2S:Tb phosphor recorded in the temperature range of 93–500 K with a heating rate of 0.52 K s−1 shows five prominent glow peaks. Comparison of the glow curves exhibited by different samples prepared with varying firing conditions reveals some interesting results. In this phosphor capture centers are mainly formed due to variable valency activators, trace impurities and point defects, which create defects in the sub-lattice. The observed TL spectra suggest a multiplicity of electron and hole traps. The main peak that observed at 150 K is attributed to point defects arising out of sulfur vacancies. These vacancies give rise to electron traps, which are found to be associated with terbium centers. This is confirmed by the monochromatic glow curves observed at wavelengths corresponding to the characteristic terbium emission (5D37Fn, 5D47Fn). Removal of this glow peak under H2S firing indicates the localized character of the concerned centers.  相似文献   

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