氚化钛中氦的热解析

氚以金属氚化物贮存形式过程中，会衰变生成氦-3，从而影响金属氚化物的使用性能。文中采用热解析方法研究了不同贮存周期氦在金属氚化物中的能量状态的变化情况。     

Comprehensive research about the cooperative up-conversion luminescence of the ytterbium-doped oxyfluoride vitroceramics

The cooperative up-conversion blue luminescence of Yb^{3+} ion-doped oxyfluoride vitroceramic material (Yb:FOV) and the influence of co-doped Ho^{3+} ion, when excited by a 960 nm diode-laser, are studied in this paper. A strong blue 479.1 nm up-conversion luminescence of the Yb:FOV material is discovered. It is found that the 479.1 nm luminescence results from the cooperative up-conversion of the coupled states of the Yb^{3+}－Yb^{3+} clusters formed by two adjacent Yb^{3+} ions. The measured cooperative up-conversion luminescence main peak 479.1 nm of this paper is different from the characteristic fluorescence main peak of the Tb^{3+} ion positioned at about 495－504 nm wave-range. Our result coincides with all the published correct papers, whose cooperative up-conversion luminescence main peaks of the direct Yb^{3+}－Yb^{3+} clusters are all positioned at about 476－480 nm wave-range. All of these indicate that the large cooperative up-conversion blue luminescence of the direct Yb^{3+}－Yb^{3+} clusters discovered in this paper is stable. It further proves that the cooperative up-conversion green luminescence may result from the Yb^{3+}-Tb^{3+} cooperative effect. In particular, the original work of this paper improves considerably on the traditional concept by the experimental facts that the blue 479.1 nm cooperative up-conversion luminescence strength of Yb(5):FOV is 230 times greater than that of fluoride glass Yb(3):ZBLAN. This is a great development to meet the practical requirements for blue up-conversion luminescence strength. This result indicates that the large cooperative up-conversion blue luminescence could be achieved excellently by using a suitable material, such as oxyfluoride vitroceramic, which provides a better chance to form better Yb^{3+}－Yb^{3+} clusters and has less relaxation to keep the more efficient up-conversion luminescence. It is also found that impurities seriously reduce the cooperative up-conversion luminescence intensity due to the cross-relaxation from the Yb^{3+}－Yb^{3+} clusters, which means that the cooperative up-conversion blue luminescence could be further improved by pure Yb^{3+} ion-doped materials that have as few impurities as possible to reduce the cross-relaxation. The large cooperative up-conversion blue luminescence of Yb(5):FOV also comes from its higher concentration (5 mol%) of activator Yb^{3+} ion which acts well because the cooperative up-conversion blue luminescence intensity varies linearly against the square of the concentration of Yb^{3+} ions in the range of 0.5－5 mol%. In summary, the great improvement of our work on cooperative up-conversion blue luminescence results from the comprehensive enhancement of the factors of better-coupled chance of the Yb^{3+}－Yb^{3+} clusters, less cross-relaxation, better concentration contribution of Yb^{3+} activator, non-saturation, and better up-conversion luminescence efficiency.     

High-Density Read-Only Memory Disc with Ag11In12Sb51Te26 Super-Resolution Mask Layer

A novel read-only memory (ROM) disc with an Ag11ln12Sb51Te26 super-resolution mask layer is proposed and investigated for the first time to our knowledge. The carrier-to-noise ratio of more than 40 dB could be obtained from small pits (380nm), which are below the readout resolution limit (400nm), in our dynamic setup with a wavelength of 632.8 nm and numerical aperture of 0.40. Dependences of carrier-to-noise ratio on readout power,readout velocity and film thickness are studied. The results show that the optimum film thickness is 20-50nm and the corresponding carrier-to-noise ratio is more than 40dB at readout power of 4mW and readout velocity of 2m/s in our experiment. The super-resolution readout mechanism for this ROM disc is also discussed.     

Effect of Magnetic Field and Equilibrium Flow on Rayleigh-Taylor Instability

We investigate the effect of a finite equilibrium flow and magnetic field on the Rayleigh-Taylor instability. It is found that the equilibrium flow only makes a frequency shift of perturbation and the growth rate of the Rayleigh-Taylor instability remains unchanged. However, the magnetic field can change the growth rate and, in particular,a very strong magnetic field suppresses the growth rate.     

Single Cell Element of Chalcogenide Randoul Access Memory Fabricated with the Focused Ion Beam Method

A singie cell element of chalcogenide random access memory was fabricated by using the focused ion beam method.The contact size between the Ge2Sb2Te5 Phase change film and the top electrode film is about 600nm (diameter) and the contact area is caiculated to be 0.28μm^2.The thickness of the phase change film is 83nm.The current-voltage characteristics of the cell element are studied using the home-made current-voltage tester in our laboratory.The minimum threshold current of about 0.6mA is obtained.     

Intermolecular interaction potentials of methane－argon complex calculated using LDA approaches

The intermolecular interaction potential for methane－argon complex is calculated by local density approximation (LDA) approaches. The calculated potential has a minimum when the intermolecular distance of methane－argon complex is 6.75 a.u.; the corresponding depth of the potential is 0.0163eV which has good agreement with experimental data. We also have made a nonlinear fitting of our results for the Lennard-Jones (12-6) potential function and obtain that V(R)=143794365.332/R^{12}-3032.093 / R^6 (R in a.u. and V(R) in eV).     

Intermolecular Interaction Potentials of CH4-Ne Complex Calculated with Local Density Approximation Methods

The intermolecular interactions potentials for two configurations of CH4-Ne complex are calculated with localdensity approximation methods in the frame of density functional theory. It is found that the calculated potentialshave two minima when the distance between the carbon atom of CH4 and the Ne atom takes R = 5.80a.u.and 6.20a.u. for both the two configurations. For the edge configuration, the corresponding depth of thepotential is 0.0669536eV and 0.0671416eV. For the face configuration, the corresponding depth of the potentialis 0,0737956 eV and 0.0645506 eV. The global minimum occurs at R = 5.80 a.u. for the face configuration with adepth of the potential 0.0737956eV. The depths of our calculation are in better agreement with the experimentaldata than the quantum chemical calculation approach~ while the position of minimum potential for our calculationis underestimated.     

Functional Integral Approach to the Transition Temperature of Attractive Interacting Bose Gas in Traps

The functional integral approach (FIA) is introduced to study the transition temperature of an imperfect Bose gas in traps. An interacting model in quantum statistical mechanics is presented. With the model we study a Bose gas with attractive interaction trapped in an external potential, We obtain the result that the transition temperature of a trapped Bose gas will slightly shift upwards owing to the attractive interacting force. Successful application of the FIA to Bose systems is demonstrated.     

A Comparison of Different Measures for Dynamical Event Mean Transverse Momentum Fluctuation

Various measures for the dynamical event mean transverse momentum fluctuation are compared with the real dynamical fluctuation using a Monte Carlo model. The variance calculated from the G-moments can reproduce the dynamical variance well, while those obtained by subtraction procedures are approximate measures for not very low multiplicity. Фpt, proposed by Gadzicki M and Mrowczynski S [Z. Phys. C 54 (1992)127], can also serve as an approximate measure after being divided by the square root of mean multiplicity.