Vol. 28, No. 5 (1979)
1979, 167 (5): 1-9. doi: 10.7498/aps.28.1
Since the discovery of Ag-O-Cs photocathode, its mechanism of photoemission has remained enigmatic. The role of silver colloidal particles is important for the explana-tion of photoemission in long wavelength region. This paper presents a general review of the role of silver colloidal particles in the literatures, such as experiments by Лахомов et al. We come to a conclusion that the photoelectric emission of Ag-O-Cs photocathode above 4000? comes from small silver colloidal particles in the film of Cs2O.
1979, 167 (5): 10-23. doi: 10.7498/aps.28.10
In this paper, the rule of photoemission from the small silver colloidal particles in the film of Cs2O is discussed, and the formulas of energy distribution of photoelectrons, photoelectric current and quantum yield are derived. The theoretical curves of energy distribution of photoelectrons, long wavelength response and quantum yield of Ag-O-Cs photocathode are compared with experimental results. It is found that for the long wavelength response the equivalent diameters of small colloidal particles are about 31?.The problems of the treatment of Cs, the additional silvering process and the ques-tion about Fowler curve are also discussed and explained.
1979, 167 (5): 24-31. doi: 10.7498/aps.28.24
This paper presents a scheme for electro-optic frequency shifting. In this scheme linearly polarized light of output from CO2 laser passes through a electro-optic modula-tor and retroaction-cycle laser amplifer, under the condition of no increased harmonic components exist, the convertion efficiency of the shifting can be raised greatly. This work suggests that electro-optic frequency shifting possesses potentiality of wide appli-cation. In the experiments on checking the effect of the frequency shifting, the experi-mental device is simplifed by auto-collmating round-trip of the light beam and space delaying the modulated signal. The frequency components of the frequency shifted light is analysed by using simple method of frequency beating.
It is shown that the optical Eabi precession model developed by Feynman, Vernon and Hellwarth for two-level systems can be extended not only to discuss the two-photon resonant coherent interaction, but also to the case of three photons. Using this model and the adiabatic following approximation, the third-order polarization expression in an intense and (or) resonant optical field is obtained, which differs from that obtained by perturbation theory. The saturation phenomena in the third-order resonant non-linear effects are also discussed.
1979, 167 (5): 40-47. doi: 10.7498/aps.28.40
A diagram which not only considers the transition of the structural type hut also describes the rule of change of Tc in the A-15 compounds is given in this paper. From this diagram it can be seen that compounds with very high Tc(>25K) are not likely to exist in the A-15 series considered. In the Nb series, Nb3Ge probably has the highest Tc; in V series, the Tc can still be expected to be raised (>17.1K), the Tc of V3Ge is likely to be raised to above 12 K. Examining the case of Nb3Si, one can not get the optimistic estimation as that of Geller. It is considered that Nb3Si of A-15 type obtained by present new technology is a non-ideal structure formed at the expense of the normal stoichiometric ratio or by a change of the ordinary atomic volume. On the basis of the relationship between Tc and radii ratio and on consideration of the radii ratio required by the ideal A-15 structure, the point of view presented in this paper does not agree with the various predictions that the Nb3Si might have a high Tc(>23 K).
1979, 167 (5): 48-58. doi: 10.7498/aps.28.48
The variational approximation method developed by Bogolyubov et al. is generalized to treat the dynamical problems of superconductor tunneling system, which results in establishing the approximate expressions, in second quantization representation, for the equation of motion, the. Hamiltonian of superconductor tunneling system and the operators of tunneling current in this variational approximation scheme. The Hamil-tonian obtained, H = HL + HR + HT + WT, consists of three parts: HL describes the behaviours of the metal on the left hand side of the sample; while HR the behaviours of the metal on the right hand side; and HT+WT the coupling between them. HL and HR are commutable with each other, and their expressions are the same as two isolating metals, except that the states of single electron are slightly mixed. The formula of matrix elements of HT is identical with that of Bardeen. The effect of WT is approxi-mately 10000 times less than that of HT, hence WT may be neglected. It is demonstra-ted that as far as the first order terms in our variational approximation method is con-cerned, the model Hamiltonian assumed by Cohen et al. applies, while Prange's treat-ment for this problem is proved to be inappropriate.
THE DIFFRACTION AT A STRAIGHT EDGE IN OPTICAL SYSTEM WITH ABERRATION UNDER PARTIALLY COHERENT ILLUMINATION
1979, 167 (5): 59-71. doi: 10.7498/aps.28.59
This paper deals theoretically with the influences of various kinds of mutual co-herence function and the degree of coherence on the distribution of straight-edge generated image field. Indicating the close connections between the illuminating con-dition and image formation, we thus obtain the reliable method to select the optimal illuminating condition. Based on our theoretical calculation on optical system with aberration, it is shown that the radial intensity distribution of the straight-edge generated imagery can reflect sensitively the quality of the optical system. This can be adopted as the quality criterion for practical optical system under partially cohe-rent illumination.
1979, 167 (5): 72-76. doi: 10.7498/aps.28.72
The spectrum of NIII has been studied in the region of 2000-680? by using a two meter normal incidence vacuum spectrograph and a condensed discharge as light source. Experimental results indicate the evident effect of the pressure of light source on the appearance of NIII spectral lines. Thirty-one new spectral lines are observed. A new energy level, 2s2p4d2D5/2, is found, and the energy value of the level 2s2p4d2D3/2 is revised.
1979, 167 (5): 77-85. doi: 10.7498/aps.28.77
In this article, through summarizing experimental data of shock-wave compression for thirty-four metallic elements, we have obtained a generally applicable empirical expression for the reduced Hugoniot curve, which describes the law of shock-wave compressions for metallic elements. In treating these data, the principle of corresponding state was employed. By utilizing the obtained reduced Hugoniot curve and basing on the Debye theory, we have derived a generally applicable equation of state for metallic elements under high pressures. We used this equation of state to calculate the pressure-compression curves for fifteen metallic elements (magnesium, iron, copper, etc). The comparison shows that the calculated values are in good agreement with experimental data.
In this paper, a study has been made of proton implantation and annealing behavior of GaAs. The single crystal wafers used in the implantation were oriented typically at 1-3° away from (100), and doped with Sn to 5×1017-1×1018cm-3. The implantation was carried out at room temperature in a proton accelerator and ion implantation machine with an energy of 8×104-2×106eV. Following bombardment, the implanted area was delineated by means of an A-B etchant, and the penetration depth of proton xj was determined. The xj values obtained can be related to the implantation energy E as follows xj= (8.716×10-4+4E-1)E1.365,where Xj is in ?, E in eV. The maximum lateral spread of the proton XL as a function of energy was also, determined, and found to be ～104? when E>3×105eV. The proton implanted samples were annealed at 150-800℃ for 5 min. A X-ray double crystal difractrometer was used to characterize the recovery of strain, and a electrometer was used to determine the resistance variation with annealing temperature. The results showed that the critical dose φ* for amorphous layer formation after proton implantation was ～1016cm-2, and the recovery of strain began at 150°, and virtually stopped at 450°. In the temperature range 150-450°, there were no significant variation in implanted resistance. The recovery of resistance oecurred only at higher temperatures. The project range of proton Rp, the electron stopping power Se(E), the nuclear stopping power Sn(E), and the mechanism of annealing of implanted proton in GaAs are discussed on the basis of the present experimental results.
THEORETICAL INTERPRETATION OF THE ENHANCEMENT OF NEUTRON DIFFRACTION IN AN α-LiIO3 SINGLE CRYSTAL UNDER THE ACTION OF A DC FIELD
1979, 167 (5): 96-106. doi: 10.7498/aps.28.96
We have noticed in α-LiIO3 single crystals the following experimental facts: (1) Using the conoscopic observation method, it was found the contrast of layer imperfections increasing with the strength of a dc field. (2) Changes take place in the x-ray topography under the action of a dc field. (3) The grown-in spatial variation of lattice parameters were found and measured by an x-ray double-crystal spectrometer. Based on these observations, we infer that space charges (carriers, impurity ions and vacancies) are accumulated at the defects of macroscopic scale, which in turn produces a gradient of lattice parameters under the action of a dc field. We calculated the neutron Bragg scattering cross section for a distorted single crystal using the Born approximation and taking into account the extinction at the same time. Therefrom, the enhancement of diffraction in an α-LiIO3 crystal under the action of a dc field were qualitatively interpreted with good agreement.
This paper describes the growth condition of PeOOH in the solution of ferrous sulphate with NaOH or NH4OH as precipitant. The crystal forms were observed with electron microscope. The phase composition and phase boundaries were determined by X-ray diffraction. When the precipitant is NH4OH or NaOH, the two phase diagrams of the FeOOH growth in the acid region are similar, but in the alkaline region they are different.
This artiele is the summary of the methods of the magnetic field design of the CT-8 Takamak. We analized the influence of all kinds of stray field on the equilibrium of the plasma tour, and discussed the requirement which should be satisfied by the magnetic field (especially, stray field) and developed a optimization method. We also analized the possibility to maintain the equilibrium in the process of temperature raising.