动态MOCVD法在Ag／Ni复合基体上连续制备YBCO超导带

本报道用ＭＯＣＶＤ方法在以１５ｃｍ／ｈｒ速度连续走带的Ａｇ／Ａｉ复合基体上制备ＹＢＣＯ超导带的结果。所有ＹＢＣＯ超导带的Ｊｃ值为１．３×１０＾４Ａ／ｃｍ＾２；样品主相为ＹＢＣＯ１２３，呈强烈ｃ－轴取向，其衍射峰的摇摆曲线半高宽约为２．８°；另外，还含有少量Ｙ２ＢａＣｕＯ５和ＢａＣｕＯ２杂相，本还用ＳＥＭ和ＥＤＸ对样品沉积层进行了观测分析。     

ZnCdTe-ZnTe多量子阱的光泵受激发射

本文报导了ＺｎＣｄＴｅ－ＺｎＴｅ多量子阱的受激发射机理．阈值时（Ｊｔｈ）受激发射峰相对于激子吸收峰的能量差（１９ｍｅＶ）与激子束缚能接近．激发光强度在３Ｊｔｈ～４．８Ｊｔｈ之间变化时，该能量差随激发光强度的变化规律与激子—激子散射过程的理论结果符合得很好，从而把该材料在上述激发光强内的受激发射机理归结为激子－激子散射过程     

TOROIDALSHEARFLOWDRIVIENINSTABILITY

ＴＯＲＯＩＤＡＬＳＨＥＡＲＦＬＯＷＤＲＩＶＩＥＮＩＮＳＴＡＢＩＬＩＴＹＬ．ＨｕａｎｇＮ．ＤｉｎｇＧ．Ｄ．ＪｉａｎＳｏｕｔｈｗｅｓｔｅｒｎＩｎｓｔｉｔｕｔｅｏｆＰｈｙｓｉｃｓ，Ｐ．Ｏ．Ｂｏｘ４３２，Ｃｈｅｎｇｄｕ６１００４１，ＣｈｉｎａＡＢＳＴＲＡＣＴ...     

二维核磁共振谱解析及其应用

２ＤＮＭＲ在波谱学的化学应用中占据首要位置。本文简述了ＣＯＳＹ，ＬＲＣＯＳＹ，ＣＯＳＹＤＥＣ，ＳＥＣＳＹ，ＤＱＣ－ＣＯＳＹ，ＲＣＴ，ＩＮＡＤＩＱＵＡＴＥ，ＲＥＬＡＹ，ＩＮＶＥＲＳＥ，ＮＯＥＳＹ，ＨＯＥＳＹ，ＯＨＡＨＡ，ＲＯＥＳＹ，ＨＭＱＣ，ＨＭＢＣ等谱的形状，指认步骤及其应用。     

Research on the UV Dielectric Coatings with High Damage Threshold

ＲｅｓｅａｒｃｈｏｎｔｈｅＵＶＤｉｅｌｅｃｔｒｉｃＣｏａｔｉｎｇｓｗｉｔｈＨｉｇｈＤａｍａｇｅＴｈｒｅｓｈｏｌｄＧＡＯＨｕａｉｌｉｎＳＨＡＮＹｕｓｈｅｎｇＷＡＮＧＮａｉｙａｎ（ＣｈｉｎａＩｎｓｔｉｔｕｔｅｏｆＡｔｏｍｉｃＥｎｅｒｇｙ，Ｐ．Ｏ．Ｂｏｘ...     

单源溶液超声波雾化MOCVD法在Ag基体上制备YBCO膜

本报道了用单溶液超声波雾化ＭＯＣＶＤ工艺在金属Ａｇ基体上制备了ＹＢＣＯ超导膜的结果。将Ｙ（ＴＭＨＤ）３、Ｂａ（ＴＭＨＤ）２和Ｃｕ（ＴＭＨＤ）２按要求比例溶于四氢呋喃中，经超声波雾化，通过毛细管送入蒸发室，随即进入沉积室，在Ａｇ基体上沉积ＹＢＣＯ。该技术有效地简化了ＣＶＤ过程，提高了所制样品的再现性。ＸＲＤ分析表明，ＹＢＣＯ膜具有较好的ｃ－轴取和向单相性。     

书评

书评ＡＩＰＨＡＮＤＢＯＯＫＯＦＣＯＮＤＥＮＳＥＲＭＩＣＲＯＰＨＯＮＥＳＴｈｅｏｒｘＣａｌｉｂｒａｔｉｏｎａｎｄＭｅａｓｕｒｅｍｅｎｔｓＧｅｅｒｇｅＳ．Ｋ．Ｗｏｎｇ，ＴＯｎｙＦ．Ｗ．Ｅｍｂｌｅｔｏｎ主编３２１＋ＸＶｌｌ页（ＡｍｅｒｉｃａｎＩｎｓｔｉｔｕ...     

用MOCVD法在YSZ衬底上制备YBCO膜

用低压ＭＯＣＶＤ多源法在单晶ＹＳＺ和具有双轴取向ＩＢＡＤＹＳＺ的金属基带上沉积了ＹＢＣＯ膜,它们的Ｊｃ（７７．３Ｋ,０Ｔ）分别为～２×１０６Ａ／ｃｍ２和～７×１０４Ａ／ｃｍ２．分析了本试验中的Ｊｃ差别原因．在单晶ＹＳＺ上ＹＢＣＯ高Ｊｃ数值显示了用ＭＯＣＶＤ制备涂层膜导体的潜力     

书评

书评ＡＣＴＩＶＥＣＯＮＴＲＯＬＯＦＮＯＩＳＥＡＮＤＶＩＢＲＡＴＩＯＮＣｄｉｎＨＨａｎｓｅｎ与ＳｃｏｔｔＤＳｎｙｄｅｒ合著ｘｘ＋１２６７页，１９９７第一版Ｅ＆ＦＮＳｐｏｎ，ａｎｉｍｐｒｉｎｏｆＣｈａｐｍａｎ＆Ｈａｌｌ，ＣｈｅｒｉｔｏｎＨｏｕｓｅ，Ｎｏｒ...     

用同步辐射光研究CO在Cs/Ru(100)表面的吸附

（ＣＯ＋Ｃｓ）／Ｒｕ（１０１０）共吸附的体系中,ＣＯ分子由于受Ｃｓ原了强烈影响,分子轨道发生重新杂化组合,ＣＯ分子原来在清洁Ｒｕ（１０１０）表面上结合能位于７．５７ｅＶ处相重叠的５σ和１π轨道对应谱峰分裂为两峰结合能分别位于６．３和７．８ｅＶ处,其中６．３ｅＶ处的谱峰来自ＣＯ分子１π轨道的一支,它显示出该分子轨道沿衬底〈００１〉晶向的镜面反对称性,ＣＯ分子１π轨道的另一支和５σ轨道在结合能７．８ｅ     

Stationary States and Modulational Instability of Coupled Two-Component Bose-Einstein Condensates in a Ring Trap

We investigate modulational instability (MI) of a coupled two-component Bose-Einstein condensates in a rotating ring trap. The excitation spectrum and the MI condition of the system are presented analytically. We find that the coupling between the two components strongly modifies the MI condition, and the MI condition is phase-dependent. Furthermore, we discuss the effect of MI on both density excitation and spin excitation. If the inter- and intra-component interaction strengths are all equal, the MI causes density excitation but not spin excitation, and if the inter- and intra-component interaction strengths are different, the MI causes both density excitation and spin excitation. Our results provide a promising approach for controlling the stability and excitation of a rotating two-component Bose-Einstein condensates by modulating its coupling strength and interaction strength.     

Quinary excitation method for pulse compression ultrasound measurements

A novel switched excitation method for linear frequency modulated excitation of ultrasonic transducers in pulse compression systems is presented that is simple to realise, yet provides reduced signal sidelobes at the output of the matched filter compared to bipolar pseudo-chirp excitation. Pulse compression signal sidelobes are reduced through the use of simple amplitude tapering at the beginning and end of the excitation duration. Amplitude tapering using switched excitation is realised through the use of intermediate voltage switching levels, half that of the main excitation voltages. In total five excitation voltages are used creating a quinary excitation system. The absence of analogue signal generation and power amplifiers renders the excitation method attractive for applications with requirements such as a high channel count or low cost per channel. A systematic study of switched linear frequency modulated excitation methods with simulated and laboratory based experimental verification is presented for 2.25 MHz non-destructive testing immersion transducers. The signal to sidelobe noise level of compressed waveforms generated using quinary and bipolar pseudo-chirp excitation are investigated for transmission through a 0.5 m water and kaolin slurry channel. Quinary linear frequency modulated excitation consistently reduces signal sidelobe power compared to bipolar excitation methods. Experimental results for transmission between two 2.25 MHz transducers separated by a 0.5 m channel of water and 5% kaolin suspension shows improvements in signal to sidelobe noise power in the order of 7–8 dB. The reported quinary switched method for linear frequency modulated excitation provides improved performance compared to pseudo-chirp excitation without the need for high performance excitation amplifiers.     

Photon-emission properties of quantum-dot-based single-photon sources under different excitations

The photon-emission efficiencies and photon indistinguishabilities of a single-photon source, which employs a cavity coupled with a quantum dot, are studied under above-band and resonant excitations. The results are obtained by solving master equations and by applying the quantum regression theorem. According to the study, the photon indistinguishability increases with the Purcell factor under resonant excitation, which is consistent with the increase in emission efficiency; however, these two figures of merit are inconsistent for the above-band excitation scheme. Moreover, the efficiencies, defined as the average photon number emitted in one excitation cycle, are almost the same for the two different excitation schemes, whereas the excitation power needed to reach that efficiency is much lower under resonant excitation than that for above-band excitation. These results will be helpful in improving the performances of the applications concerning indistinguishability and efficiency.     

Virtual excitation type surface polaritons on anisotropic media

We discuss the nature of a new type of surface polariton which occurs on anisotropic media, involving a photon coupled to a surface virtual excitation. Dispersion curves are calculated for α-quartz, where both real excitation type and virtual excitation type surface polaritons are predicted. The dispersion curves for virtual excitation surface polaritons are found to remain at small wavevector, and the endpoints of the dispersion curves terminate on the bulk polariton dispersion curves in the two media. The virtual excitation surface polaritons which occur on gyromagnetic and gyrodielectric media are also noted.     

Some simple mechanisms of multiphoton excitation in many-level systems

Results are reported on coherent monochromatic multiphoton excitation in many-level systems, which are representative for some of the basic mechanisms for atomic and molecular multiphoton processes. Numerical solutions are discussed that use the Floquet and quasi-resonant approximations in the framework of the URIMIR program package. The excitation schemes include direct three-photon excitation, two-photon excitation with diagonal coupling, Göppert-Mayer-type two-photon processes, multiphoton excitation with off-resonant inter-mediates, and practically irreversible coherent excitation into dense spectral structures. Several interesting phenomena are observed, such as nonlinear line shifts and broadenings of multi-photon resonances of relevance for multiphoton spectroscopy and almost constant intermediate population inversions, potentially useful for laser design. The accurate numerical results are compared with approximate solutions from perturbation theory, and with simple analytical solutions from Rabi-type formulae.     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

方差评估在幅值限制脉冲优化中的应用

改进了现有针对限制幅值磁共振脉冲的优化设计方法,在脉冲优化过程中加入对脉冲激发效率方差的评估．该方法能有效改善脉冲带宽激发的不均匀性．并探讨了改进方法中不同的方差权重系数以及脉冲幅值限制条件对于优化效果的影响,以获得最佳的脉冲优化效果．     

Effect of dielectronic recombination excitation in the solar chromosphere-corona transition region

The intensities of lines emitted from the solar chromosphere-corona transition region and observed on the earth are calculated by considering excitation of electrons to the upper level caused by electron-impact excitation and dielectronic recombination excitation processes. For the lines under investigation, the electron-impact deexcitation rates are negligibly small in comparison with spontaneous transition probabilities. Hence, electrons from the upper level deexcite through spontaneous transition only, emitting photons of wavelength corresponding to the energy difference between two levels. To determine the contribution of dielectronic recombination excitation (DRE) to the excitation mechanism, the calculations are repeated with exclusion of DRE. It is found that DRE contributes significantly and that its contribution may be much larger than that of electron-impact excitation.     

Indirect optical cooperative excitation of two-particle electronic excitations in doped organic molecular crystals

A theory on the indirect optical cooperative excitation of a two-particle electronic excitation composed of one host exciton and one guest-molecule one-particle electronic excitation through one electric dipole-moment active singlet guest molecule one-particle electronic excitation is developed by considering the nonradiative coupling bstween one- and two-particle electronic excitations.The complex dielectric tensor and the corresponding absorption coefficient are found out, which are expressed in terms of the Fourier-transform of the retarded Green function: The derived formulas are discussed in an explicit form for the one-dimensional model of the doped organic molecular crystal. Within the framework of ths one-dimensional model also the conditions for the existence of the host exciton-guest molecule one-particle electronic excitation bound states are established and discussed.     

The time dependence and efficiency of excitation of three-quantum coherence in proton spectroscopy of proteins

The time dependence and efficiency of excitation of three-quantum (3Q) coherence is examined for the peaks that are commonly observed in 'H NMR 3Q spectra of proteins. The algebraic expressions for the various contributions to each 3Q coherence are tabulated. Plots of the excitation efficiency versus the length of the excitation period are shown. These results provide guidelines for optimizing the length of the 3Q excitation period to obtain either a wide range of 3Q signals in the spectrum or the excitation of specific 3Q signals with maximum efficiency.