Vol. 45, No. 8 (1996)
1996-04-20
GENERAL
1996, 45 (8): 1249-1254.
doi: 10.7498/aps.45.1249
Abstract +
Effects of the Aharonov-Bohm flux to the soliton in a one-dimensional ferromagnetic ring are investigated. The effects on the peak, the width, the rest energy and the effective mass of the soliton by the Aharonov-Bohm flux are shown.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
1996, 45 (8): 1255-1263.
doi: 10.7498/aps.45.1255
Abstract +
An algorithm to construct the generator of gauge transformation for a system with singular higher-order Lagranian in field theories is given. Starting from generating functional of Green function in phase space, the Ward identities in canonical formalism for the constrained Hamiltonian system are deduced. It is pointed out that the quantal canonical equation for such a system deffers from the classical canonical equation, arising from the fact that Dirac conjecture is valid. The quantization for a generalized dynamical system which can be equivalent to Chern-Simons theory is given. With preliminary application of canonical Ward identities to such a system, some relationships among the vertices and propagators for the fields can be deduced without carrying out the integration for canonical momenta in phase space path integral.
NUCLEAR PHYSICS
1996, 45 (8): 1264-1274.
doi: 10.7498/aps.45.1264
Abstract +
Electron acceleration in an axisymmetric radially-polarized laser field has been studied by both analytical and numerical calculations. The relationships concerning acceleration and field parameters are investigated together with the discussion on the transimitting characteristics and quality of electron beam.
ATOMIC AND MOLECULAR PHYSICS
1996, 45 (8): 1275-1279.
doi: 10.7498/aps.45.1275
Abstract +
The populations of np forbidden transition states for two-step excitation of Na atom have been obtained by appling the static field of strength 167 V/cm. We have obtained lifetimes of np(n = 19-23) states by the method of delaying ionization in pulsed electric field, and have compared the calculation values with the measured data. The influence of applied fields and environmental radiation on the determination of the lifetimes of the highly excited states were discussed.
1996, 45 (8): 1280-1286.
doi: 10.7498/aps.45.1280
Abstract +
The polarized characteristic of multiphoton process can be used to assign the symmetries of electronic states and vibrational structures. In this paper the polarizing ratios of some kinds of degenerate three-photon transitional tensors are calculated. Besides, the three-photon resonant polarizing ioniza-tion spectra of ethylbenzene are measured. The highly excited electronic state which is responsible for the transition is referred as A" and the vibrational structures of this electronic state are also obtained.
1996, 45 (8): 1287-1291.
doi: 10.7498/aps.45.1287
Abstract +
The expression for the diarnagnetic susceptibility derived using gauge invariant molecule orbital is applied to the calculation of π eletcrons of C60,C70,C76,C78,C82 and C84. The numerical results show that the fullerenes have large diarnagnetic susceptibility, and that the diarnagnetic susceptibility of some fullerenes, such as C70 and C76 etc., has remarkable anisotropy.
CLASSICAL AREA OF PHENOMENOLOGY
1996, 45 (8): 1292-1296.
doi: 10.7498/aps.45.1292
Abstract +
In this paper, a group of concave grooves with micron and submicron width was designed and fabricated by using photolithography, electron-lithography and ion etching techniques, and their diffractive performance was investigated in experiment. The experimental measured data show that the grooves have the feature of vector's diffraction.
1996, 45 (8): 1297-1303.
doi: 10.7498/aps.45.1297
Abstract +
A scheme for the preparation of a Fock state is proposed. We study two lights interacting in a Kerr media with self-phase modulation. The signal light and the probe light whose initial states are both coherent states will be entangled via interaction, then when a quadrature component of the probe light is measured, the photon number distribution of the signal light is modulated. Repeating the process, we find the signal will collapse into a Fock state finally, and the physical principle of this evolution is based on the cross-phase modulation, the self-phase modulation may hinder the preparation of a Fock state.
1996, 45 (8): 1304-1312.
doi: 10.7498/aps.45.1304
Abstract +
Emission spectra of a pair of effective two-level atoms interacting with two modes of the cavity field through Raman interaction are studied, where the interaction of each atom with the field may be different. The spectra with two modes of the cavity field being initially in various number states are analysed in detail. It is found that emission spectra manifest following new properties: When mode 1 of the cavity field is in vacuum state and the other is in the weak field , the spectrum shows symmetric ten peaks and six peaks alternately, with the increase of R=g2/g1, which reflects the different Raman interacting intensities of two atoms with the cavity field more sensitively compared with the spectrum of two atoms in a single-mode cavity. The spectrum with 01=1, n2=50 and n1 = 50, n2=1 reflects the different positions of mode 1 and mode 2 of cavity field interacting with two atoms through Raman process. Finally, the symmetric 16-peaks structure of the spectrum is explained.
1996, 45 (8): 1313-1318.
doi: 10.7498/aps.45.1313
Abstract +
A theoretical model has been established based on the solution of the rate equations for the erbium-doped fiber ring laser(EDFL). Analytic solutions for the threshold pump power, the output power, the slope efficiency and optimum erbium-doped fiber length of EDFL are obtained. The physical explanations have been given for the results.
1996, 45 (8): 1319-1325.
doi: 10.7498/aps.45.1319
Abstract +
Idealizing the ultrashort pulse electron beam modulated by radio-frequency as a delta function on time scale, we calculate the coherent synchrotron radiation emitted by the electron micropulse in a rectangular waveguide with the method of eigenmode expansion. We find that when the frequency of radiation is the integral times of the radio frequency ωrf, the radiation field pattern will appear as "pure" eigenmodes of waveguide. In addition, we analyse the frequency performance of the coherent synchrotron radiation and the slippage effect. And finally, the gain of a rectangular electron pulse amplifying the radiation is deduced.
1996, 45 (8): 1326-1330.
doi: 10.7498/aps.45.1326
Abstract +
In the high efficiency and small signal region, we investigate theoretically the efficiency enhancement mechanism of far infrared free electron laser (FIR-FEL) with a reverse tapering waveguide. The numerical simulatiion with single particle model suggests that this kind of waveguide whose gap is gradually narrow along z axis substantially heightens the FIR-FEL efficiency.
1996, 45 (8): 1331-1336.
doi: 10.7498/aps.45.1331
Abstract +
Based on the principle of Fresnel diffraction and Gerchberg-Saxton algorithm, an effective method for designing binary optical diffractive elements (BODE) is presented. The objective light distribution, generated by a BODE designed by this method, is not sensitive to laser mode. A BODE, used in quenching treatment of CO2 laser, was designed and fabricated by photolithography and ion etching techniques. The element could transform a CO2 laser beam into rectangle beam shape with dimensions 12 mm×2 mm. The experimental results are satisfactory for the quenching treatment .
1996, 45 (8): 1337-1343.
doi: 10.7498/aps.45.1337
Abstract +
In this paper, a threshold model for an end pumped Ho3+ laser is developed by using quasi-three-level laser model. The relations between threshold and design parameters are analyzed. A general principle for design low threshold Ho3+ laser is given. The results are also valid for other quasi-three-level laser systems.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1996, 45 (8): 1344-1349.
doi: 10.7498/aps.45.1344
Abstract +
A numerical method is given for calculating the high energy electron absorptive structure factors. The numerical results so obtained are fitted with the analytic Doyle-Turner form using combined least-square and simulated annealing methods. As an illustration for the fitting, we have given results for five elements Be, Al, As, Ag and Au. In particular we have given the relative and absolute error curves for Al.
1996, 45 (8): 1350-1358.
doi: 10.7498/aps.45.1350
Abstract +
In the present paper the moderate temperature (MT) phase of the Ge(111) surface, which was obtained by quenching the Ge(111) sample from about 300 1C to room temperature, has been studied by means of ultra-high-vacuum scanning tunneling microscopy (STM) . It has been found that in addition to diffusion of individual Ge adatoms, the most prominent feature of the MT phase is the concerted motion of Ge adatoms along the walls of the 2×2 domains. The moving adatoms may form either open strings or closed loops. Such concerted motion of Ge adatoms on the Ge(111) surface was predicted previously and has been of much theoretical interests, recently. However, this is the first experimental observation of such motion. Our study shows that the motion is not a result of STM tip interference and that it is always along the directions. On the basis of our STM observations as well as the results of the recent theoretical works some discussions on the characteristics of the concerted motion are given.
1996, 45 (8): 1359-1365.
doi: 10.7498/aps.45.1359
Abstract +
A systematic study of the effect of physical ageing and cooling rate on a-relaxation peak are carried out in PVC. It was said that a-peak and Tg are not the same concept. Both are closely connected with amorphous state, but show different behaviours in the same pre-treatment conditions: varying physical ageing time in sub- Tg or changing cooling rate from Tg + 20℃ to room temperature . Some interesting results were obtained as follows:When Tg lowers with increacing ageing time or decreacing cooling rate, a-peak temperature (Tα) keeps constant. On the other hand, the intensity of the a-peak decreases. This behaviour shows that a- relaxation peak is not a typical linear anelastic internal friction peak, as there is a quenching peak added on it.A detail discussion will be given in this paper.
1996, 45 (8): 1366-1371.
doi: 10.7498/aps.45.1366
Abstract +
The etch pits of dislocations in Bi12GeO20 crystal at (100), (110) and (111) planes have been studied by means of chemical etching. The pattern of etch pits are very special compared with the common cubic system crystal, and we have analyzed it with theory of symmetry group. The patterns of etch pits by theoretical analysis are in conformity with the experiment. It shows that the pettern of etch pits of dislocations consists of {112} planes. It is clear that the habitual plane of crystal of Bi12GeO20 crystal is {112} plane.
1996, 45 (8): 1372-1379.
doi: 10.7498/aps.45.1372
Abstract +
Based on Ref. [3](Acta Physica Sinica, 44(1995), 987(in Chinese)), we have derived the relations between lattice Green's functions for the semi-infinite square lattice and the infinite square lattice. The partial density of states and the formation condition of the surface localized state are calculated by virtue of lattice Green's function for the semi-infinite square lattice.
1996, 45 (8): 1380-1389.
doi: 10.7498/aps.45.1380
Abstract +
We have studied the ordering processes of Ag on Si (111) by LEED using a homemade high re-solution spot profile measuring equipment. The results show that the growth processes of Ag 31/2 domain satisfy scaling symmetry. They are self-similar growth processes. The studies also show that the growth exponent is near 1/2 in the early stage of the growth processes. We propose a growth mechanism of Ag diffusing from Ag(111) islands to form Ag 31/2 domains. This article also suggests a way to obtain perfect surface structures in lower temperature by using light-assisted anneal.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1996, 45 (8): 1390-1395.
doi: 10.7498/aps.45.1390
Abstract +
Within the mean-field approximation, we discuss effects of the projection operator in the fermion-spin theory. The ground-state kinetic energy of the t-J model is studied, and the results show that the mean-field ground-state kinetic energy is consistent with the numerical results. The possible phase separation is also discussed.
1996, 45 (8): 1396-1401.
doi: 10.7498/aps.45.1396
Abstract +
In this paper, LMTO method is described briefly. We applied it to calculate the electronic structure of NdFe10Mo2 with interstitial N atom which is related to the tetragonal ThMn12 structure. From the variation of density of states we can obtained the magnetic moment. The function about variation of magnetic moment after nitration is discussed and campared with calculated local magnetic moment. In NdFe10Mo2 compounds with interstitial N atom, the 8j site has its minimal magnetic moment.
1996, 45 (8): 1402-1408.
doi: 10.7498/aps.45.1402
Abstract +
Raman spectra of BaTiO3 and Ce: BaTiO3 single crystals have been recorded between room temperature and 180℃. Three new bands at 986,1204 and 1480 cm-1 in the X(ZZ) Y geometry are discovered. Based upon the temperature dependence of Raman scattering cross sections, the new bands are attributed to the second-order Raman spectra of BaTiO3, while the strong asymmetry bands at 275 and 514 cm-1 in A1(TO) spectrum are confirmed to be of first order. On the basis of above results, the Raman spectra of cubic BaTiO3 and the model of phase transitions are discussed. It is found that doping with Ce in BaTiO3 lowers its Curie temperature, which agrees with the experimental results of dielectric constants.
1996, 45 (8): 1409-1417.
doi: 10.7498/aps.45.1409
Abstract +
Luminescence of Eu3+ in stoichiometric host luminescent crystal Na5Eu(WO4)4 has been studied under low temperature 20-300 K and hydrostatic high pressure 0 - 10 GPa using a diamon anvil high pressure and low temperature microspectroscopic system. We report for the pressure shift rates of spectral lines, energy levels and crystal field parameters of Eu3+ under low temperature. These pressure shift rates vary directly with temperature, and the experiment shows that the effects of temperature or pressure on the spectral lines of Eu3+ are not independent like that of R1 and R2 spectral line in ruby. According to crystal field theory, we have suggested a simplified method to derive the relations between energy levels and crystal parameters. The pressure shift rates of crystal parameters at low temperature(△Bkg/△p)T have been determined by fitting with the experimental spectral data.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
1996, 45 (8): 1418-1424.
doi: 10.7498/aps.45.1418
Abstract +
The observations of the water vapor maser emission toward the Orion - KL nebala have been carried out with the 13.7 m radio telascope at Delingha station of Purple Mountain Observatory. The maser emission is characterized by the "quiescent phase" with the peak flux density 3×104Jy, two orders lower than that during the "outburst phase". The maser action in the "quiescent phase" is full saturated with the quiescent level of brightness temperature 3×1013 K. On the assumption of spherical maser and the saturated state, the hydrogen density of 8 × 1014(H2)m-3 and the population inversion of 5×105(H2O)m-3 in the masing region are derived.The Orion super water vapor maser spectrum consists of emission in three symmetric velocity intervals centered at the velocity 10 km·s-1. This may imply that there are symmetric outflows or expanding shells with constant velocities in the masing region.
