Vol. 39, No. 10 (1990)
ATOMIC AND MOLECULAR PHYSICS
The energy level structures of Rydberg slates of Ru atom in 4d7(4F) ns series and 4d7(4F) nd series are measured by means of laser resonance excitation-electric field ionization method. The relative line strengths within the multiplet of an electron configuration are calculated. The theoretical results are coincident with the experiments satisfactorily. The terms of the measured spectrum lines can be identified.
1990, 39 (10): 1536-1541. doi: 10.7498/aps.39.1536
The autoionization spectra of the 4dnp and 4dnf, J=1 series of Sr atom have been observed in the range of 59570-60300cm-1 using three-step laser excitation method. 60 lines have been obtained, most of them can be classified into six series converging to the 4d2D3/2 and 4d2D5/2 ionization thresholds, respectively. The profile of the line and configuration interaction are also discussed.
1990, 39 (10): 1542-1546. doi: 10.7498/aps.39.1542
Freon123 (CF3CHC12 and CF3CDC12) molecules are superexited by the intense IR laser pulse without tail from the TEA CO2 laser, reaching very high exited state. In the dissociation processes, it is shown that the C-C bonds having higher energy in Freon123 were mostly broken under certain experimental conditions, but only a few C-Cl bonds having lowest energy ruptured. The main products were C2F6, and H2C=C=CH2 and it's substitution derivatives. It is indicated by the relationship between the relative yields of productions and laser energy flux that intramolecular V-V energy transfer of Freon123 is nonrandomizational.
TIME RESOLVED STUDIES OF STATE TO STATE VIBRATIONAL ENERGY TRANSFER (Ⅰ)——SELF-COLLISION PROCESSES OF IDIONE MOLECULES
1990, 39 (10): 1547-1554. doi: 10.7498/aps.39.1547
This paper presents an experimental procedure to study state-to-state collisional dynamics by using tunable and pulsed laser techniques and timeresolved and dispersed fluorescence method. The decay processes of electronically and vibrationally excited iodine, B3Πou+(v＇=19), to the adjacent vibrational states in self-collisional events have been directly observed in experiments. The rate constants for the state-to-state vibrational transfer obtained are, kv(19→18) = (2.21±0.33)×10-11cm3s-1mol-1 and kv(19→20) = (1.44±0.20)×10-11cm3s-1mol-1. These results are in satisfactory agreement with the principle of detailed balance. In addition, the collision-free lifetimes and the radiationless quenching rate constants in B(v＇= 19) were also obtained in the experiments.
CLASSICAL AREA OF PHENOMENOLOGY
ENHANCED SQUEEZING OF THE INTRACAVITY LIGHT FIELD PRODUCED IN PARAMETRIC AMPLIFICATION VIA LASER INJECTION
1990, 39 (10): 1555-1562. doi: 10.7498/aps.39.1555
For the squeezing of intracavity light fields produced in a parametric amplifier located within a cavity, we use laser injection which can compensate the effects of the cavity losses and therefore reduce the random force on the squeezing, and thus generate a large amount of intracavity squeezing near the threshold of oscillation.
In this paper, the characters of thermal fracture and optical distortion pump-induced in Nd: glass slab lasers are described. Both the calculation formulas and the experimental results are given. The calculation results are well consistent with the experiments.
1990, 39 (10): 1570-1572. doi: 10.7498/aps.39.1570
The continuously tunable sum-frequency generation of 367.3-379.4 nm of the Rh·6G dye laser and the Q-YAG laser was obtained in β-BaB2O4 crystal. The sum-frequency output energy is about 2 mJ, and the conversion efficiency is about 12%. The influence of the non-collinear propagation on the output energy and conversion efficiency of turn-frequency generation are also discussed.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
THE TIME-SPACE STRUCTURE EVOLUTION OF TOKAMAK PLASMA UNDER THE MUTUAL INTERACTIONS OF TEARING MODE WITH TRANSPORT PROCESS
1990, 39 (10): 1573-1582. doi: 10.7498/aps.39.1573
This paper presents a theoretical study of the evolution of tearing modes in tokamak. plasma. Combining the tearing mode with a 1-D transport code, computer simulations are conducted. The result shows that the transport process plays an important role in the development of the macro-instability. Under the mutual interaction of macro-instability and transport process, the MHD pattern of tokamak presents various space and time structure. That also gives rise to the time and space behavior of other plasma parameters such as temperature and density.
1990, 39 (10): 1583-1590. doi: 10.7498/aps.39.1583
A method of calculating the temperature profile of high-pressure sodium electric arcs using the diffusion approximation for the radiation flux density is described. Account is taken of energy transfer due to thermal conduction, emission and absorption of radiation. The method has been applied to calculate the temperature profile for a sodium vapor pressure of 250 Torr and the calculated temperature distribution is compared with the result of experimental measurement.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
In this paper, the strain and stress field produced by an edge dislocation are expressed by means of continuous dislocation distribution. The stresses inside and outside the core of the edge dislocation are obtained. The dislocation distribution of infinitesimal strength is expressed by crystal defect gauge field, which are calculated under certain gauge condition. In side the core, the stresses are finite when r goes to zero. The singularity of stresses is removed. Finally, the energy of the edge dislocation are calculated.
1990, 39 (10): 1599-1601. doi: 10.7498/aps.39.1599
Clean surfaces of Tb4O7 crystal have been studied by a surface profile imaging technique cm the atomic scale. The formation of a 60° mixed dislocation due to electron radiation on the(111) surface was observed in-situ.
A statistical theory of delayed fracture in a wide range of stress (1》(ασ)/(Kt)》1) has been proposed. The fundamental idea is that microcrack stochastically evolves based on the atomic bond mechanism leading to fracture. The microcack evolution equation is given. The microcrack distribution function, fracture probability, reliability, the statistical distribution function of fracture strength and fracture life and their statistical average value are derived.
1990, 39 (10): 1614-1618. doi: 10.7498/aps.39.1614
In situ observation of the ferro-elastic transition in BNN crystal is carried out with the convergent polarized interference pattern, it reveals that the crystal transforms from bioaxies to uniaxies in heating with an inflection point Ts at 250±20℃. The transition is of the continuous and diffuse type. A large hysteresis about 20-30℃ is show by the fact that heating and cooling curves are distinct above 210℃. The twins (ferro-elastic domain) disappear and reappear in accordance with the time of phase transition. The density of the twins influences the inflection point Ts of the phase transition and the degree of hysteresis leading to decrease in Ts and increase in the hysteresis. The defects and microscopic compositional inhomogeneities are the main cause for the diffuse of the phase transition.
1990, 39 (10): 1619-1623. doi: 10.7498/aps.39.1619
Using diamond-anvel cell high pressure equipment, the phase transition of Cd1-xMnxSe under high pressure has been measured by optical absorption and X-ray diffraction methods, It has been found that the phase transition is irreversible. Under common pressure, Cd1-xMnxSe has wurzite structure, but it transforms to Nad structure under high pressure. When the pressure is removed, Cd1-xMnxSe becomes zinc blend structure. In addition, the relation between the pressure of phase transition and component x is also obtained.
The wetting transition in a closed system between two parallel walls with fixed temperature, volume and number of particles is discussed. It is shown that a closed system is different in wetting aspect from an open system. The conclusion in agreement wirh the investigation via Monte-Carlo techniques is obtained analytically.
1990, 39 (10): 1635-1639. doi: 10.7498/aps.39.1635
Under the assistance of magnetic field, the electron cyclotron resonance effect generates a high density plasma in a large spaceregion This offers an beneficial condition for large area diamond films deposition. By using a mixture of methane (CH4) and hydrogen (H2), a diamond film of 5 cm diameter has been grown on silicon substrate under the pressure about 3 Torr which is considerably lower than the pressure in all other methods recently used. In view of the spacial extent of the plasma, we see that it is possible to further increase the area of deposited diamond film. The growth condition of diamond film in gas phase deposition under the pressure of 0.5 to 50 Torr has been discussed on the basis of analyzing the optical emission spectrum of the plasma.
1990, 39 (10): 1640-1646. doi: 10.7498/aps.39.1640
The geometrical configurations of (100)-oriented (Si)n/(Ge)n (n = 1-6) strained superlat-tices on Si1-xGex(x = 0-1) substrates are calculated by using Keating model. The influence of substrate on the growth of the superlattices is discussed. The calculations indicate that proper choice of substrate Si1-xGex is beneficial to the growth of (Si)n/(Ge)n superlattices.
1990, 39 (10): 1647-1652. doi: 10.7498/aps.39.1647
LiV2O4, with spinel structure, is prepared under vacuum by heat-treatment of Li0.5VO2 obtained by chemical extraction of 0.5 lithium from the layered compound LiVO2. Similar treatment of Li0.465VO2 results in a cation-deficient spinel Li0.93V2O4. X-ray powder diffraction data show that LiV2O4 is only different slightly from Li0.93V2O4 The preliminary test of the experimental cell by using LiV2O4 as positive electrode is made.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1990, 39 (10): 1653-1660. doi: 10.7498/aps.39.1653
Under the extended defect potential approximation, the electronic wave function which is a function of the PV defect energy has been derived using a tight binding Koster-Slater Green function technique. Taking the experimental value of the defect energy level as input parameter, the obtained wave function describes quantitatively the data of the electron paramagnetic resonance and electron-nuclear double resonance. Especially, the hyperfine interaction constants of the four nearest neighbor atoms around the vacancy given by the theory, are in good agreement with the experiment.
1990, 39 (10): 1661-1664. doi: 10.7498/aps.39.1661
Thermally induced metastable defects in reactive sputtered a-SiGe:H films are studied by conductivity σ(T) and heterojunction capacitance-voltage (C-V) measure ments.
1990, 39 (10): 1665-1670. doi: 10.7498/aps.39.1665
A number of surface analysis techniques, including XPS, UPS and HREELS, are used to study oxygen adsorption on GaP(111) surfaces.Initial oxygen adsorption is found to be saturated at an exposure around 104L. Information concerning surface electron structure variation in this stage, such as surface band bending, chemical shifts, etc. has been obtained. It is found that this stage of oxygen adsorption is related to surface defects. Proper annealing treatment can remove the surface defects along with the adsorbed oxygen. Such oxygen adsorption followed by annealing might be a way for defect removal in surface engineering.
1990, 39 (10): 1671-1675. doi: 10.7498/aps.39.1671
The phase boundary relationships for site-bond percolation and diluted magnetic system transition are established by generalizing the universal relationships of pure site and pure bond percolations. As compared with other methods used to treat the problems of site-bond percolation and diluted magnetic system transition, it can be found that the relationships given in the present paper has some advantages, such as, simplicity, convenient to use, and accuracy. Especially, it has a clearer physical meaning.
1990, 39 (10): 1676-1683. doi: 10.7498/aps.39.1676
One of the authors had pointed out that the heavy fermion system is a kind of Kondo system in which localized f-electrons can change with temperature. The f-electrons are bound in a narrow band near Fermi level. Using this model, the relation between the susceptibility and temperature is deduced and the susceptibility anomaly is explained in this paper. The calculated results of susceptibility for all the eight heavy fermion system coinside with the experimental data. The strong sample dependence of the susceptibility of the heavy fermion system has also been discussed.
1990, 39 (10): 1684-1690. doi: 10.7498/aps.39.1684
Some aspects on the application of second order diffraction of a monochrometer in laboratory EXAFS measurement are studied. Significant distortions in measured X-ray absorption fine structure occur when there are impurities' emission lines on the continuum spectra m the investigated energy range. A method for correcting that distortion is proposed. As the EXAFS amplitude decreases, which is caused by the application of second order diffraction of a monochrometer, how to obtain correct structural parameters is also discussed.
1990, 39 (10): 1691-1696. doi: 10.7498/aps.39.1691
Co-adsorption of CO and potassium on Fe(110) is investigated by HREELS. We find three CO adsorption states, with different C-O stretching frequencies. When θk=0.03, the three loss peaks are ascribed to three kinds of interactions i.e., short-range, medium-range and long-range interaction. When θk = 0.06, the long-range interaction adsorption state disappears, but the short-range state dominats. All C-O stretching frequencies shift to higher wavenum-ber with the increasing of CO exposure. CO-Fe loss peak disappears with the increasing of potassium atoms on the surface.