Vol. 37, No. 8 (1988)
1988-04-20
CONTENT
1988, 37 (8): 1227-1235.
doi: 10.7498/aps.37.1227
Abstract +
We report the generation of turnable IR stimulated emission covering 3.39-3.46 μm, by using a new exciting mechanism called "two-step hybird exciting" in sodium molecular-atomic system. We analyse and discuss carefully this IR emission. The computed relative intensity of the IR emission varies with the pumping deturning. The computational results matched well with experimental data.
1988, 37 (8): 1236-1243.
doi: 10.7498/aps.37.1236
Abstract +
The microtube target with side jet burner is designed. Strong population inversion is observed along the whole side jet burner between the energy leveles of MgXI Is3p 1P00 and Is4p 1P00 while the average laser irradiance reached about 3.5×1013W·cm-2 on the inner wall of the microtube targets. The corresponding environment average electron temperature 470-520 eV and density of 2×10cm-3 of plasma at the inversion area is measured. The possible mechanisms of population inversion under the average high temperature condition has been analysed.
1988, 37 (8): 1244-1253.
doi: 10.7498/aps.37.1244
Abstract +
The emission spectra in collision process between He2+ and Ne, Ar have been measured using optical methods, by Optical Multichannel Analysis. System. The experimental results demonstrate that there are three channels of excitation in these collision systems: double-electron capture into excited states, single-electron capture into excited states and direct excitation of projectile and target by incident ion impact. Emission cross sections of HeI, HeII, NeI, NeII and ArI, ArII have been obtained from calculations. Some comparisons of emission cross sections between He2++ Ne and He2++Ar have been made.
1988, 37 (8): 1254-1259.
doi: 10.7498/aps.37.1254
Abstract +
Recent experimental results on generating of excited states in collisions of single, double charged ions with He, Ne, Ar are presented. Laboratory energy range of the beams of Heq+, Arq+ (q=1,2) ions are (70-170)×q keV. The optical measurement was performed by Optical Multichannel Analysis System, the wavelength range covered was 200-800 nm. Different processes of excitation have been observed in single and double charged ions collisions with atoms. The dependence of emission cross sections on the charge number of incident ions and potential energy defect is discussed.
1988, 37 (8): 1260-1266.
doi: 10.7498/aps.37.1260
Abstract +
The photofragnentation dynamics of ammonia molecules following pulsed UV laser excitation of ground state to the two lowest levels ν′2 = 0 and 1 (ν2 vibrational mode) of their ?1(A"2) electronic excited state has been investigated by monitoring thetime-of-flight spectra of the nascent H-atom products. The spectra confirm recent revised estimates of the quantity D00(H-NH2) = 4.645 eV and reveals that the majority of the accompanying NH2 (X2B1) fragments are formed vibrationally unexcited, but with high levels of rotational excitation specifically concentrated about the a-inertial axis. The NH2(X) fragments resulting from photodissociation via the ν′2 = 1 level of NH3(?) carry a higher level of internal excitation and show an inverted population distribution over the N = Ka rotational levels.
1988, 37 (8): 1267-1274.
doi: 10.7498/aps.37.1267
Abstract +
In this paper, Unruh-DeWitt type particle detector is reformed to detectors with instant response. After this reformation, all ideal particle detectors become equivalent, although they respond differently to different quantum state. This kind of detectors are designed to detect the quantity 2>, just as Davies desired. Furthermore, a useful method for calculating the instant response function for a detector with monopole coupling and moving arbitrarily in a Minkowski vacuum is presented.
1988, 37 (8): 1275-1283.
doi: 10.7498/aps.37.1275
Abstract +
An integral eigenequation is derived for the strongly collisional plasma by applying the gyrokinetic technique. An analytical proof of the absolute stability for the drift wave in a slab geometry with finite magnetic shear is presented. The macroscopic motion of electrons parallel to the ambient magnetic field is taken into consideration and Lee-Chen-Nevins method is adopted in the proof.
1988, 37 (8): 1284-1290.
doi: 10.7498/aps.37.1284
Abstract +
The MHD equation is used to study the stabilization of low frequency drift waves driven by density gradient of plasma in a hot electron plasma. The dispersion relation is derived, and the stabilizing effects of hot electrons are discussed. The physical mechanism for hot electron stabilization of the low frequency plasma perturbations is charge uncovering due to the hot electron component, which depends only on a, the ratio of Nb/Nt, but not on the value of βh. The hot electrons can reduce the growth rate of the interchange mode and drift wave driven by the plasma, and suppress the anomalous plasma transport caused by the drift wave. Without including the effect of βh, the stabilization of the interchange mode requires α≈2%, and the stabilization of the drift wave requires α≈40%. The theoretical analyses predict that the drift wave is the most dangerois low frequency instability in the hot electron plasma.
1988, 37 (8): 1291-1297.
doi: 10.7498/aps.37.1291
Abstract +
The defects and the nonradiative recombination of photogenerated carriers in a-Si:H and a-SiNx:H films are studied by using infrared spectrometer, spectrophotometer, photoacoustic Spectrometer and positron annihilation life-time spectrometer from various respects.
1988, 37 (8): 1298-1306.
doi: 10.7498/aps.37.1298
Abstract +
Based on the theory of correlated-basis-functions, and with the "big molecular" model, we have presented a new theory of hydrogen chemisorption on metal surfaces. Through the variational numerical calculation with respect to the parameter of position of adatom, we obtained chemisoption energies, electron densities, and equilibrium distances for the hydropen chemisorption on metals Al (rs = 2.07), Mg (rs = 2.66), Li (rs =3.28) and Na (rs =3.99) We also made a comparison with some other representative theories.
1988, 37 (8): 1307-1314.
doi: 10.7498/aps.37.1307
Abstract +
Conductance of high-valence ions in montmorillonite solid electrolyte was investigated with various chemical and physical ways, in particular, by the methods of electrical property measurment and electrochemistry. The results show that montmorillonite is a practical and promising solid electrolyte material. Some mechanisms on migration for high-valence ions in montmorillonite are discussed.
1988, 37 (8): 1315-1325.
doi: 10.7498/aps.37.1315
Abstract +
In this paper, the method of continously distributed dilocations is used to obtain the exact solutions of distribution functions D1(η) and D2(η) for single pileup of screw dislocations formed aginst an obstacle and double pileups of sorew dislocations between an inclusion and an obstacle under action of an applied stress while existing inhomogeneity. At the pileup tip near the obstacle, D1(η) and D2(η) have inverse square root singularity and D2(η) has-ω power singularity at pileup tip near the inclusion. The double pileups is used to represent the antiplane shear crack terminating at the interface of inclusion and the stress intensity factors are obtained. The solutions presented are valid for 02/G1<∞ and the results are discussed.
1988, 37 (8): 1326-1332.
doi: 10.7498/aps.37.1326
Abstract +
A generalized Villain formula is introduced. In this general Gaussian approximation, the topological properties of the electromagnetic loop for compact QED in four dimensions with an action which is the admixture of two terms with any different periodicities are investigated. The common properties of the phase structure, including two kinds of different partial confinement phases and a two-photon phase, of this model in the whole parameter space are discussed. By using the modified Migdal-Kadanoff group transformation, the phase diagrams for the cases of (N1, N2) = (l,5), (1,6), (1,7) are obtained. The numerical results are consistent with the theoretical analysis.
1988, 37 (8): 1333-1340.
doi: 10.7498/aps.37.1333
Abstract +
A quantum theory of Cerenkov radiation in gas medium is estiblished by means of the first-order perturbation of quantum feild theory. The results show that there are some characteristics different from Cerenkov radiation of liquid and solid. The main features of this Cerenkov radiation are as follows: (1) Line emission, asymmetric profile and small red shift; (2) The radiation angle is independent of frequency and decreases along with increasing of the speed of incident charged particles: (3) No speed threshold of the charged particles exists; (4) No matter whether and atom is at ground state or at excited state, the pro-bility of Cerenkov radiation is identical. The theoretical predictions coincide with the experiments.
BRIEF REPORT
1988, 37 (8): 1341-1344.
doi: 10.7498/aps.37.1341
Abstract +
We have analysed the level structrue of perturbed Rydberg series 1P10 of Al Ⅱ using the multichannel quantum defect theory (MQDT). The analysis shows that the main series 3snp1P10 is perturbed so strongly by the doubly excited state 3p4s1P10 such that the latter has entirely distributed into the main series and does not correspond to a single spectrum line any more. The experimental energy levels are well reproduced and the energy levels for n≤50 are calculated.
1988, 37 (8): 1345-1349.
doi: 10.7498/aps.37.1345
Abstract +
The defect imaging contrast on the section topographs for the crystal of potassium acid phthalate (KAP) has been studied, using the synchrotron radiation. The experimental results show that the diffraction contrast due to defects in the crystal is considerably increased with the wavelength increasing in a certain range The dynamical theory of X-ray diffraction for homogeneously deformed crystals with average values of the strain gradient parameter βis taken to interpret the experimental results, for which the factor β teff plays an important role in the defect imaging contrast formation We propose that it is possible to choose an appropriate wavelength of synchrotron radiation which could give out higher diffraction contrast for defects in crystals.
1988, 37 (8): 1350-1356.
doi: 10.7498/aps.37.1350
Abstract +
Two ferroelectric single crystals Pb0.37Ba0.63 Nb2O6 and Pb0.30Ba0.533Na0.306Li0.028 Nb2O6,pulled from melt by Czochralski technique, have been studied. By X-ray diffraction, it has been determined that both of two crystals belong to the tetragonal system with lattice parameters a = 12.493 ?, c = 3.984 ? for PBN, and a = 12.493 ?, c=3.970 ? for Li, Na-doped PBN. All of the dielectric, elastic, and piezoelectric coefficients of the two crystals have been measured. The results show that PBN crystal possesses good piezoelectric character with d15≈108×10-12C/N. This crystal could be a promising material for piezoelectric transducers operating in the shear mode. The dielectric constants are reduced, while the Tc is enhanced obviously in PBN doped by Li and Na Ions.
1988, 37 (8): 1357-1362.
doi: 10.7498/aps.37.1357
Abstract +
The critical properties of a generalized mixed spin model (T-H model) on two dimensional hexagonal lattice are studied by using real space renormalization group and mean field methods. An Ising, a tricritical and a first-order phase transition fixed point are found. At last, some exact results of this model are found by using star-triangle transformation method.
1988, 37 (8): 1363-1367.
doi: 10.7498/aps.37.1363
Abstract +
Via a reconsideration of a simple model for bipolarons, we have shown that in order to-keep the total energy of the model system to be a stable minimum, a new phonon coherent state should be introduced as a result of the electron-phonon interaction. Thus it could be in-fered that the reduction effect of phonons is much weaker and the range of the singlet bipo-laronic state as the stable ground state configuration is more extensive than what the previous authors considered.
1988, 37 (8): 1368-1372.
doi: 10.7498/aps.37.1368
Abstract +
The resistance changes,△R/R, of fifteen different kinds of Pd-, Cu-. Ni-, and Fe-based amorphous alloys in the presence of elastic and plastic deformations have been measured. The resistivity ρ, density d and proportional limit σp for several amorphous alloys as functions of shrinkage ψ have also been determined. The results on the curve of p-ε and △R/R-ε indicate the existence of elastic, anelastic, and the plastic regions. Stress p and △R/R increase linearly with strain e in the first two regions. Density, resistivity and proportional limit vary with ψ obviously, however, their changes are very small after ψ>30%. Mechanism of the plastic deformation occurring in amophous alloys is also discussed.
1988, 37 (8): 1373-1375.
doi: 10.7498/aps.37.1373
Abstract +
The permeability of polycrystalline iron thin films implanted with different doses of boron ions rises nonmonotonously with increasing dose, while the 57Fe conversion electron Mossbauer spectra of the films have shown the formation of amorphous metallic alloy. The results favour the critical defect density model of amorphous state formation.
1988, 37 (8): 1376-1380.
doi: 10.7498/aps.37.1376
Abstract +
Twin boundaries were determined in both R-phase and martensite of NiTi shape memory alloy using group decomposition theory. It was found that there are four variants existing in the R-phase with {110}p and {100}p twin planes between the variants. The four variants may form three types of self-accommodation groups. While in the martensite phase, there may be three variants with {110}p twin planes between the variants. The three variants have four possibilities to form a self-accommodation group. These results are in good agreement with the experiment.
1988, 37 (8): 1381-1385.
doi: 10.7498/aps.37.1381
Abstract +
In lower-hybrid current drive Tokamak, the waves can drive radial energy flux of resonant electrons, which is composed of a directional flux and a conduction-like flux. When the waves are strong enough, the effects of the radial energy flux may be comparable to that of the Coulomb collisions, and the picture of current drive will be changed.
1988, 37 (8): 1386-1393.
doi: 10.7498/aps.37.1386
Abstract +
The shortcomings in previous treatments of boundary and junction conditions for the self-consistent density profile are analysed carefully. In order to reflect precisely the factual boundaries, the vacuum boundary and the plasma rest upstream are connected to the upper and lower density profile shelves by the self-similar solutions respectively, and the perfect matching at the sonic point is realized. Our analytic results agree well with computer simulation
1988, 37 (8): 1394-1400.
doi: 10.7498/aps.37.1394
Abstract +
The chaotic behaviours of bend crystal channel under the action of periodic field was predicted. The properties of global bifurcation in the system and the condition for occurrence of Smale horseshoes were analyzed, and we showed that the process of approaching chaotic state is the dechanneling process of a particle, and the channeling effect and channeling radiation would exhibit intrinsic stochasticity. The results provided possible theoretical analysis for quantitative discription of channeling effect and channeling radiation.
