In this paper a more simple and flexible analytical method for indexing X-ray powder patterns of monoclinic substances by using computer is proposed. The lattice parameter b can be obtained from the repeat number m of δ value of every pair of diffraction lines in δ-m chart and their linear relationship. By the reducing procedure the reciprocal lattice is projected on the a*-c*plane and the angle of each pair of reciprocal vectors can be calculated from the Qnkl data of each triplet of reciprocal points. According to the repeat number M in β-M chart the monoclinic angle β can be obtained and then the lattice parameters a and c can be calculated. Finally the indexing of the entire diffraction patterns is made by iterative correction method for indexing powder patterns. The computer program of the analytical method is given. The indexing of two monoclinic substances nickel acetate hydrate (C4H6NiO)4·4H2O) and potassium tungstate (K2WO4) has been made by using this method, the result proves that the method is fairly applicable.
In this paper a more simple and flexible analytical method for indexing X-ray powder patterns of monoclinic substances by using computer is proposed. The lattice parameter b can be obtained from the repeat number m of δ value of every pair of diffraction lines in δ-m chart and their linear relationship. By the reducing procedure the reciprocal lattice is projected on the a*-c*plane and the angle of each pair of reciprocal vectors can be calculated from the Qnkl data of each triplet of reciprocal points. According to the repeat number M in β-M chart the monoclinic angle β can be obtained and then the lattice parameters a and c can be calculated. Finally the indexing of the entire diffraction patterns is made by iterative correction method for indexing powder patterns. The computer program of the analytical method is given. The indexing of two monoclinic substances nickel acetate hydrate (C4H6NiO)4·4H2O) and potassium tungstate (K2WO4) has been made by using this method, the result proves that the method is fairly applicable.
The effecte of isothermal and isochronal annealing on the structures of the metal glasses Co50.7Ni19.5Fe7.8Si6B16 and Co42.9Ni27.3Fe7.8Si8B14 have been investigated by the wide angle and the small angle X-ray scattering methods. The experimental results obtained show two types of structure relaxation: The relaxation associated with topographical short range ordering (TSRO) and the relaxation associated with chemical short range ordering (CSRO), and give particularly the direct evidence of the CSRO relaxation process in the amorphous states. The atomic co-operative process of the two types of structure relaxation, and their coexistence and correlation are discussed preliminarily.
The effecte of isothermal and isochronal annealing on the structures of the metal glasses Co50.7Ni19.5Fe7.8Si6B16 and Co42.9Ni27.3Fe7.8Si8B14 have been investigated by the wide angle and the small angle X-ray scattering methods. The experimental results obtained show two types of structure relaxation: The relaxation associated with topographical short range ordering (TSRO) and the relaxation associated with chemical short range ordering (CSRO), and give particularly the direct evidence of the CSRO relaxation process in the amorphous states. The atomic co-operative process of the two types of structure relaxation, and their coexistence and correlation are discussed preliminarily.
We used the smooth pertubation method to treat the problem of Alfven wave propagation in double, plasma system. The wave propagation is analysed for two cases. One is that when the dense homogeneous beam moves in an inhomogeneous background plasma and the another one is the opposite situation.The results are briefly discussed.
We used the smooth pertubation method to treat the problem of Alfven wave propagation in double, plasma system. The wave propagation is analysed for two cases. One is that when the dense homogeneous beam moves in an inhomogeneous background plasma and the another one is the opposite situation.The results are briefly discussed.
Based on s-d interaction, we consider RKKY interaction existing between two magnetic impurities, and propose a new double impurities scattering model. According to this model, when an impurity spin makes spin flip scattering, its spin as an inner free degree will be confined by other impurities' spin, where the RKKY correlation exists between them. Because of this correlation, it will suppress its spin flip scattering. This suppression, coupled with the Kondo logT term, causes a local maximum. In this paper we have calculated all possible 'DIS' diagrams (the double impurities self-energy diagrams) and found a term A/(T02-T2) contribute to the Kondo resistance, where A is a positive constant, T0 is some critical temperature. When T≤T0, this formula is meaningless. This theory is essentially different from the previous molecular field theory. Because it does not depend on the magnetic order in alloys, so, when T≥Tc (Tc is magnetic phase transion temperature), this mechanism still works but the molecular field theory does not. This mechanism is a paramagnetic effect. We have compared this theory with experimental curves of Cd-Mn (its impurity density is 0.1～0.01 at.%). We find that the agreement with experiments is good. Finally, we consider that this mechanism is the main reason to quench the Kondo log T divergence even for very dilute magnetic alloys in low temperature.
Based on s-d interaction, we consider RKKY interaction existing between two magnetic impurities, and propose a new double impurities scattering model. According to this model, when an impurity spin makes spin flip scattering, its spin as an inner free degree will be confined by other impurities' spin, where the RKKY correlation exists between them. Because of this correlation, it will suppress its spin flip scattering. This suppression, coupled with the Kondo logT term, causes a local maximum. In this paper we have calculated all possible 'DIS' diagrams (the double impurities self-energy diagrams) and found a term A/(T02-T2) contribute to the Kondo resistance, where A is a positive constant, T0 is some critical temperature. When T≤T0, this formula is meaningless. This theory is essentially different from the previous molecular field theory. Because it does not depend on the magnetic order in alloys, so, when T≥Tc (Tc is magnetic phase transion temperature), this mechanism still works but the molecular field theory does not. This mechanism is a paramagnetic effect. We have compared this theory with experimental curves of Cd-Mn (its impurity density is 0.1～0.01 at.%). We find that the agreement with experiments is good. Finally, we consider that this mechanism is the main reason to quench the Kondo log T divergence even for very dilute magnetic alloys in low temperature.
The phonon spectra of crystalline solids with bcc, fcc and diamond structures were calculated using the recursion method. The result of the calculation demonstrated the feasibility of this method in treating complicated systems. This work also provided a base for applying the method to study the dynamics and electronic structure of amorphous systems.
The phonon spectra of crystalline solids with bcc, fcc and diamond structures were calculated using the recursion method. The result of the calculation demonstrated the feasibility of this method in treating complicated systems. This work also provided a base for applying the method to study the dynamics and electronic structure of amorphous systems.
In the present work the linear Muffin-tin orbital method (LMTO) is studied. In applying this method to the calculations of some molecules, the parameters have been carefully chosen, the effects of the choice of parameters on the self-convergence and the final results have been investigated. Due to the limitation of the computer available, the calculations have been carried out only for diatomic molecules. The results obtained agree fairly well with experimental results.
In the present work the linear Muffin-tin orbital method (LMTO) is studied. In applying this method to the calculations of some molecules, the parameters have been carefully chosen, the effects of the choice of parameters on the self-convergence and the final results have been investigated. Due to the limitation of the computer available, the calculations have been carried out only for diatomic molecules. The results obtained agree fairly well with experimental results.
The 4T2,4T1, and 2E levels of Cr3+ ion on the mirror-site in an alexandrite crystal are in relation to the laser operation of that material. The 4T2 (or 4T1) level splits into three sublevels. In order to determine the energy levele diagram of Cr3+ ions in chrysoberyl, the splitting of the 4T2 and 4T1 are calculated. We have discussed the anisotropic transition intensities of corresponding absorption bands and have found a method to fit the spectra. Furthermore, the values of the parameters K1 and K2 that represent the magnitude of the splitting are obtained, and the crystal field energy level diagram of BeAl2O4:Cr3+(II), labelled by the irreducal representations of point group C3, is given.
The 4T2,4T1, and 2E levels of Cr3+ ion on the mirror-site in an alexandrite crystal are in relation to the laser operation of that material. The 4T2 (or 4T1) level splits into three sublevels. In order to determine the energy levele diagram of Cr3+ ions in chrysoberyl, the splitting of the 4T2 and 4T1 are calculated. We have discussed the anisotropic transition intensities of corresponding absorption bands and have found a method to fit the spectra. Furthermore, the values of the parameters K1 and K2 that represent the magnitude of the splitting are obtained, and the crystal field energy level diagram of BeAl2O4:Cr3+(II), labelled by the irreducal representations of point group C3, is given.
The theory of the optical multistability by two-photon resonant interaction is investigated. The nonlinear medium inside a Fabry-Perot cavity is in two-photon resonance with the laser beam. The two-photon equation of state including dynamical Stark shift and relaxation parameters is obtained and studied under mean-field approximation. The equations for both Fabry-Perot cavity and ring cavity take basically the same form. The physics mechanisms resulting in optical multistability are also studied. It has been shown that the combined effects of Kerr switching and saturation absorption switching can lead to two-photon optical double-bistability, tristability as well as bistability. Furthermore, the criterion conditions under which double-bistability or tristability can occur are given and discussed. Finally, the phase-conjugated reflectivity by two-photon four-wave mixing is also shown to exhibit multistability as well as hysteresis.
The theory of the optical multistability by two-photon resonant interaction is investigated. The nonlinear medium inside a Fabry-Perot cavity is in two-photon resonance with the laser beam. The two-photon equation of state including dynamical Stark shift and relaxation parameters is obtained and studied under mean-field approximation. The equations for both Fabry-Perot cavity and ring cavity take basically the same form. The physics mechanisms resulting in optical multistability are also studied. It has been shown that the combined effects of Kerr switching and saturation absorption switching can lead to two-photon optical double-bistability, tristability as well as bistability. Furthermore, the criterion conditions under which double-bistability or tristability can occur are given and discussed. Finally, the phase-conjugated reflectivity by two-photon four-wave mixing is also shown to exhibit multistability as well as hysteresis.
We propose here a multichannel theory on inverse two-electron recombination processes (i.e., inverse resonance radiative-recombination processes). As a specific example, we analyze the recent high-resolution laser spectroscopic measurements on excited barium atoms by Safinya and Gallagher, illustrating that accurate experimental spectroscopic data can be utilized to assess the accuracy of theorectical calculations on inverse two-electron recombinations. Through the detailed balance relation, it is equivalent to assess the accuracy of theoretical calculations on two-electron recombination processes- this will be a more basic test on theoretical results for eachappropriate symmetric block in partial-wave expansions.
We propose here a multichannel theory on inverse two-electron recombination processes (i.e., inverse resonance radiative-recombination processes). As a specific example, we analyze the recent high-resolution laser spectroscopic measurements on excited barium atoms by Safinya and Gallagher, illustrating that accurate experimental spectroscopic data can be utilized to assess the accuracy of theorectical calculations on inverse two-electron recombinations. Through the detailed balance relation, it is equivalent to assess the accuracy of theoretical calculations on two-electron recombination processes- this will be a more basic test on theoretical results for eachappropriate symmetric block in partial-wave expansions.
The samarium-nickel binary system has been studied by X-ray diffraction, differential thermal and metallographic analyses. The phase diagram has been determined. In the system the following eight intermetallie compounds were observed: Sm3Ni(decomposes at 664℃), SmNi (M. P. 1079℃), SmNi2 (decomposes at 1034℃), SmNi,(decomposes at 1135℃), Sm2Ni7 (decomposes at 122℃), SmNi4 (decomposes at1282℃), SmNi5 (M. P. 143℃), and Sm2Ni17 (decomposes at 1288℃). Three eutec-tics occur: Sm,Ni-SmNi (570℃,～32 at%Ni), SmNi-SmNi2 (809℃, 53.5 at%Ni) andSm2Ni17-Ni (128℃, 94 at%Ni). Neither Sm in Ni nor Ni in Sm shows any detectablesolid solubility.
The samarium-nickel binary system has been studied by X-ray diffraction, differential thermal and metallographic analyses. The phase diagram has been determined. In the system the following eight intermetallie compounds were observed: Sm3Ni(decomposes at 664℃), SmNi (M. P. 1079℃), SmNi2 (decomposes at 1034℃), SmNi,(decomposes at 1135℃), Sm2Ni7 (decomposes at 122℃), SmNi4 (decomposes at1282℃), SmNi5 (M. P. 143℃), and Sm2Ni17 (decomposes at 1288℃). Three eutec-tics occur: Sm,Ni-SmNi (570℃,～32 at%Ni), SmNi-SmNi2 (809℃, 53.5 at%Ni) andSm2Ni17-Ni (128℃, 94 at%Ni). Neither Sm in Ni nor Ni in Sm shows any detectablesolid solubility.
By using the Collins' model, Kawamura had studied the phase transition of a two dimensional system. In this work, taking into account the molecular fraction and the presence of the 4-atom, we calculated the Gibbs free energy and studied, the influence of the percent of 4-atom on the parameters of the triple point and the critical point. We obtain a phase diagram showing three phases with a triple point and a critical point. The relation between the extent of each phase and the temperature is calculated along each transition line. The obtained results are quite analogous to the behavior of the three-dimensional substances.
By using the Collins' model, Kawamura had studied the phase transition of a two dimensional system. In this work, taking into account the molecular fraction and the presence of the 4-atom, we calculated the Gibbs free energy and studied, the influence of the percent of 4-atom on the parameters of the triple point and the critical point. We obtain a phase diagram showing three phases with a triple point and a critical point. The relation between the extent of each phase and the temperature is calculated along each transition line. The obtained results are quite analogous to the behavior of the three-dimensional substances.
Raman spectra of LiNbO3: MgO crystals has been obtained for the first time and compared with Raman spectra of pure LiNbO3 crystals. No change of the number, frequency, and relative intensity of Raman spectral lines of A1(TO) and E(TO) mode is found. There are only a very little increase in the line width. It is shown from this result that the more, intensive Raman spectral lines o,f A1(TO) and E(TO) vibrational mode are contributed by (NbO6) oxygen octahedra characteristic group of LiNbO3 crystals.
Raman spectra of LiNbO3: MgO crystals has been obtained for the first time and compared with Raman spectra of pure LiNbO3 crystals. No change of the number, frequency, and relative intensity of Raman spectral lines of A1(TO) and E(TO) mode is found. There are only a very little increase in the line width. It is shown from this result that the more, intensive Raman spectral lines o,f A1(TO) and E(TO) vibrational mode are contributed by (NbO6) oxygen octahedra characteristic group of LiNbO3 crystals.
Alloys of different nominal composition Nb3(Al1-xGex) (where x = 0.20, 0.23, 0.25 containing A15 + σ phases) have been heat-treated under high pressure up to 67kbar. With increasing treating pressure, 1) the lattice parameter of A15 phase as well as the I211/I210 of relative integral intensity of X-ray diffraction peak (211) and (210) of A15 phase having some concern with structure composition both exhibits a maximum, 2) the structure composition of A15 phase shifts toward the Nb-rich direction, 3) the superconducting transition temperature Tc decreases, while the width of superconducting transition temperature range shows a maximum. The results were discussed.
Alloys of different nominal composition Nb3(Al1-xGex) (where x = 0.20, 0.23, 0.25 containing A15 + σ phases) have been heat-treated under high pressure up to 67kbar. With increasing treating pressure, 1) the lattice parameter of A15 phase as well as the I211/I210 of relative integral intensity of X-ray diffraction peak (211) and (210) of A15 phase having some concern with structure composition both exhibits a maximum, 2) the structure composition of A15 phase shifts toward the Nb-rich direction, 3) the superconducting transition temperature Tc decreases, while the width of superconducting transition temperature range shows a maximum. The results were discussed.
The possible high pressure modifications of Lithium Iodate (LiIO3) were surveyed in the high pressure and high temperature ranges up to 40 kbar and 750℃. Two high pressure modifications have been observed. The first is found in the range of 1.5-4.9 kbars and 310-450℃, while another appears in the pressure range above 15 kbars. The phase boundries were determined by DTA and quenching method. The diagram published abroad in 1969 have been corrected and the stability of each phase at high pressures and high temperatures has been discussed.
The possible high pressure modifications of Lithium Iodate (LiIO3) were surveyed in the high pressure and high temperature ranges up to 40 kbar and 750℃. Two high pressure modifications have been observed. The first is found in the range of 1.5-4.9 kbars and 310-450℃, while another appears in the pressure range above 15 kbars. The phase boundries were determined by DTA and quenching method. The diagram published abroad in 1969 have been corrected and the stability of each phase at high pressures and high temperatures has been discussed.
The statistical properties of polarized laser speckle is discussed. An exact probability density function of integrated intensity of partially polarized laser speckle is obtained. We study by the experiment how the probability density function of integrated intensity of polarized laser speckle varies with the area of detector aperture and mean intensity.
The statistical properties of polarized laser speckle is discussed. An exact probability density function of integrated intensity of partially polarized laser speckle is obtained. We study by the experiment how the probability density function of integrated intensity of polarized laser speckle varies with the area of detector aperture and mean intensity.
Third-order nonlinear susceptibility x(3)(-ω;ω,ω,-ω) is calculated in nearly-degenerate quasi-two-level system by perturbation method. We have studied the level crossing effect in degenerate four-wave mixing and compared it with the level crossing effect in resonance fluorescence. The possibility of using level crossing effect in degenerate four-wave mixing to measure the relaxation rate of upper and lower state is pointed out.
Third-order nonlinear susceptibility x(3)(-ω;ω,ω,-ω) is calculated in nearly-degenerate quasi-two-level system by perturbation method. We have studied the level crossing effect in degenerate four-wave mixing and compared it with the level crossing effect in resonance fluorescence. The possibility of using level crossing effect in degenerate four-wave mixing to measure the relaxation rate of upper and lower state is pointed out.
The dependences of luminescence peak shift and relative emission intensity of (Zn0.85Cd0.15)S:Cu, Al phosphor on hydrostatic pressure have been studied at room temperature with a high-pressure microspectroscopic system in conjunction with the gasketed diamond anvil cell, using the methanal ethanal mixture as pressure liquid, the hydrostatic pressure ranging 1bar-66 kbar was monitored by ruby R-line shift. The emission peak E(r) of (Zn0.85Cd0.15)S:Cu, Al shift to higher energy with increasing pressure, dE(r)/dP=4:.7 meV/kbar (38 cm-1/kbar), but less strongly than does the absorption edge of the host. The relative emission intensity decreases strongly with increasing pressure, decreasing by 6% when pressure increasing from 1bar to 66 kbar. The results can be explained in terms of Al3+-Cu+ donor-acceptor pair model. Finally, we estimate that dED(Al3+)/dP+dEA(Cu+)/dP=3.7 meV/kbar (30cm-1/kbar).
The dependences of luminescence peak shift and relative emission intensity of (Zn0.85Cd0.15)S:Cu, Al phosphor on hydrostatic pressure have been studied at room temperature with a high-pressure microspectroscopic system in conjunction with the gasketed diamond anvil cell, using the methanal ethanal mixture as pressure liquid, the hydrostatic pressure ranging 1bar-66 kbar was monitored by ruby R-line shift. The emission peak E(r) of (Zn0.85Cd0.15)S:Cu, Al shift to higher energy with increasing pressure, dE(r)/dP=4:.7 meV/kbar (38 cm-1/kbar), but less strongly than does the absorption edge of the host. The relative emission intensity decreases strongly with increasing pressure, decreasing by 6% when pressure increasing from 1bar to 66 kbar. The results can be explained in terms of Al3+-Cu+ donor-acceptor pair model. Finally, we estimate that dED(Al3+)/dP+dEA(Cu+)/dP=3.7 meV/kbar (30cm-1/kbar).