Vol. 34, No. 12 (1985)
1985, 34 (12): 1521-1529. doi: 10.7498/aps.34.1521
In this article the construction of measurement system on IIT-6B Tokamak which is highly sensitive to soft X-ray fluctuation is described and the primary results presented. When the average electron temperature Te is less than 100 eV, the wave shapes of typical soft X-ray fluctuations, the disruptive instabilities, the MHD disturbances, and some other interesting phenomena have been observed.
SCALING THEORY OF ANDERSON LOCALIZATION IN DISORDERED SYSTEMS WITH SPACE MODULATIONS A REAL SPACE RENORMALIZATION GROUP APPROACH
1985, 34 (12): 1530-1538. doi: 10.7498/aps.34.1530
We developed a method of real space renormalization group transformation, suitable to handle a variety of space-modulated disordered systems. By this method, maintaining the relative space-modulation structures unchanged under transformation, we could study the critical properties of Anderson localization of these systems. By solving the RG equations for disordered metallic superlattices with finite-lattice approximation, the fixed point and critical exponent have been calculated approximately. It is found that space-modulation may change the properties of electronic localization in disordered systems to some extent.
1985, 34 (12): 1539-1548. doi: 10.7498/aps.34.1539
The effect of size and temperature on the quasiparticle density of state in small superconductorsty have been calculated by using the functional integral method. The influence of small particles embeded in oxidic layer of tunnelling junction on the Jose-phson current have also been investigated. An anomaly exhibits in the supercurrent. In addition, the quasiparticle currents of the junction have been calculated, the results obtained are consistent with the experiments.
1985, 34 (12): 1549-1558. doi: 10.7498/aps.34.1549
New criterion for symmetric properties of defect potential in semiconductors is presented. For a degenerate energy level Es, we introduce the average Es of energy splitling under stress. Es is invariant under symmetry operation of Hamiltonian. Therefore, it is straight foward to reduce the stress coefficient tensor of Es by group theoretical method. For instance, for cubic semiconductors, if the defect level ET is withdefect potential of T group symmetry, the uniaxial stress coefficient of (?(Ec-ET))/(?F) or (?(ET-Ev))/(?F) is isotropic and equal to one third of corresponding hydrostatic pressurecoefficient. The case of defect potential with C3v symmetry is also discussed.The electron (or hole) emission and capture processes of defect levels under energy splitting are analysed. The weighted average of emission rate en and capture rate cn satisfy the following relation: en=gTgc-1cnN′ce(-(Bc-BT)/kT) By measuring the stress dependence of en., various schemes for determining the symmetry property of defect potential are discussed. The transient processes under defect level splitting are also discussed. When transitions are al lowed between the splitting states, the transient is exporential with single decay time constant en-1. When transitions between different states are forbidden, the transient is decay with multi-exponential time constants. en is determined by the initial transient slope.
1985, 34 (12): 1559-1566. doi: 10.7498/aps.34.1559
A minority earlier peak is discovered in the DLTS of a silicon p+n junction doped with gold under majority carrier pulse condition. The major experimental results and systematic physical analyses is presented. We show, that the minority carrier peak is a result due to the capture of a free minority carrier tail from the side of the heavily doped region of the p+n junction at the mincrirty carrier traps in the space charge region, which is built by the built-in potential, and its subsequent emission.
1985, 34 (12): 1567-1572. doi: 10.7498/aps.34.1567
We report the observation of autoionization spectra for 5p1/2ns series of Sr, using the method of the isolated-core excitation (I. C. E.). The energy levels, quantum defects and widths have been measured for eight 5p1/2 ns states of Sr.
1985, 34 (12): 1573-1581. doi: 10.7498/aps.34.1573
We report here the results of far infrared absorption on spectra of mixed crystal Cd1-xMnxTe with different compositions x in wavenumber region of 20 to 400cm-1 and temperature region of 4.2 K to 300 K. The CdTe-like, MnTe-like reststrahlen bands and their LO-TO splitting have been resolved. A low frequency absorption band for all the samples and a quasi-local mode absorption peak for the sample with low x value have been found for the first time in the low frequency side of reststrahlen band. In addition, several two-phonon bands have also been observed on both sides of reststrahlen band. The appearence and the position of the quasi-local mode have been estimated with the lattice dynamics of defects. Other absorption bands and their probable origin have also been discussed.
1985, 34 (12): 1582-1594. doi: 10.7498/aps.34.1582
Absorption spectra, emission spectra and excitation spectra of Er3+ ions in fluoride glasses, fluorophosphate glasses and phosphate glasses were measured. The influence of glass hosts on the luminescence of Er3+ ions was explained. The effects of temperature and ion concentration on the luminescence of Er3+ ions in these host glasses were investigated, and the discussions about the intrinsieal and internal energy transfer of Er3+ ions were presented.
1985, 34 (12): 1595-1602. doi: 10.7498/aps.34.1595
Following our previous work , the influence of photo-induced refractive index change on Raman spectra of LiNbO3 crystals doped with 0.07% Fe has been further studied. Anomalous phenomenon appeared in x(zx)z and y(zy)z geometry. This can be explained as the result of interaction between the polarization electrical field of extraordinary phonon and the strong space charge field forming after photo-induced refractive index change in the crystals.
SURFACE ENHANCED RAMAN SCATTERING FROM BENZOIC ACID, SALICYLIC ACID AND P-HYDROXYBENZOIC ACID IN Ag COLLOIDS
1985, 34 (12): 1603-1612. doi: 10.7498/aps.34.1603
We studied surface enhanced Raman scattering (SERS) from Benzoic Acid (BA), Salicylic Acid (SA) and P-Hydroxybenzoic Acid (PHBA) in silver sols. The enhanced Raman spectra are recorded and analyzed. The three molecules all contain vibration of ν(C-CO2-) and two of them (SA and PHBA) contain vibration of ν(C-OH), but located at different position. Making use of this situation, we analyzed the dependance of enhancement factor on the distance and orientation of the vibration dipoles relative to the surface and also compared with the pure electromagnetic model for SERS. An apparent discrepancy were revealed. The possible origins are disscussed. We also discussed the influence of coagulation of silver particles on the enhancement factors and pointed out the way for optimizing the enhancement in silver colloid.
1985, 34 (12): 1613-1619. doi: 10.7498/aps.34.1613
Systematic experimental results for atomic magnetic moment and Curie temperature for amorphous alloys FeTmB(Tm=Ti, V, Cr, Mn, Zr, Nb, Mo, Ta, W) prepared by the drum spinning techniqul are reported. The average magnetic moment for each Ye atom is about 2.0 μB in all amorphous FeTmB alloys. The localized characteristics for Tm atom in the amorphous state is much outstanding than in the crystalline state. The average magnetic moment for each IVB(Ti), VB(V), VIB(Cr), VIIB(Mn) atom related with the number of outer electrons per atom is about 4, 5, 4, 3 μB, respectively, and is antiferromagnetic coupling with the Fe magnetic moment. The experimental data of the magnetic moment change rate dμ/dx is in good agreement with the calculated value using a mixed model. According to Friedel's VBS model the delectron states of IVB(Ti), VB(V) elements are completely above the Fermi level EF, but for the VIB(Cr), VIIB(Mn) elements they cross the Fermi level EF.
The S-K-K peak in Fe-P alloys has been studied by a vacuum Kê-pendulum. It is found that phosphorus of substitutional solid solute element strongly reduces the peak height (Qh-1), and obviously lowers the peak temperature (Tp) as well as evidently decreases the activation energy (H) of relaxation; the I-F peak height Qh-1 reduces linear-ly with an increase in phosphorus concentration to two thirds power Cp2/3 (namely thesquare of the phosphorus atom concentration on dislocation lines) when the concentration of phosphorus is below its solid solute limit in iron. The experimental results are ccnsitent with Sehoeck's theory. The mechanism of the I-F is also discussed and is attributed to the dragging by pinned non-screw (including edge) dislocation segments of a Cottrell atmosphere of interstitial solute atoms, by migration of the solute atoms and the dislocation segments moving by bowing.
POSITRON ANNIHILATION STUDY OF CRYSTAL DEFECTS DEVELOPED DURING FATIGUE PROCESS OF PURE POLYCRYSTALLINE Ni
1985, 34 (12): 1627-1633. doi: 10.7498/aps.34.1627
Positron annihilation lifetime spectra and Doppler broadening linesliapes of positron annihilation radiation energy were measured for the tension-compression fatigued Ni specimens under constant strain amplitude and for the cold rolled ones which were used for comparison. A few of the formers were selected for TEM observation. A lifetime component that can be associated with e+ lifetime in vacancy clusters developed during fatigue process was resolved by using a multi-exponential fitting method. It is 209, 255 and >300 ps on average in diferent ranges of fatigue respectively. The change of its relative intensity seems associated with increase of the concentration of the small vacancy clusters at early stage and growth of its dimension afterwards.Hence, this work provides a experimental evidence for the formation and clustering of vacancies as well as the development of a great number of jogged dislocations in fatigued Ni. The concentration of these defects were estimated by using a simple three state e+ trapping model. This work also provides a illustration of the utility of multi-exponential fitting method to complex lifetime spectra and to the above mentioned trapping model.
1985, 34 (12): 1634-1640. doi: 10.7498/aps.34.1634
Samples of Berlinite(α-AlPO4) have been grown by slow heating method in autoclave. The piezoelectric constants and elastic constants have been measured by transmission method at room temperature. In addition, the influence of various defects in crystals on electric properties were studied.
1985, 34 (12): 1641-1643. doi: 10.7498/aps.34.1641
The defects in Hg1-xCdxTe crystals are observed using HREM. Two kinds of 60° dislocation as well as the twin dislocation in the twin-plane boundary are obserred directly. It is showed that twin dislocation is the activated step of the migration of twin-plane boundary during recrystallization.
The collisional interaction between Ba and Yb is not pure dipole-dipole. The maximum of transfer cross section appears at the induced laser wavelength, which corresponds to the interatomic transition. The effect of spin interaction is observed.
1985, 34 (12): 1649-1652. doi: 10.7498/aps.34.1649
High order neutron components from Ge(lll) reflection have been measured in the region of 5—22 meV using time-of-flight method at the heavy water reactor in Beijing. The measured results have been compared with theoretical calculation and a satisfactory agreement is obtained. The results show that Ge(111) reflection suffers from a serious order contaminations below 20 meV.
1985, 34 (12): 1653-1657. doi: 10.7498/aps.34.1653
Inelastic neutron scattering spectra from C-15 phase superconducting alloys V2Hf, V2Ta, V2Hf0.8 Ta0.2, V2Zr0.5 Hf0.5 and V2Zr0.5 Hf0.33 Ta0.17 were measured by the neutron time-of-flight method, and their relative phonon densities of states were evaluated. The present results show that the phonon frequencies soften with the increase of the superconducting transition temperature Tc and harden with the decrease of the Tc, which is in agreement with our previous results of "The effect of Nb on phonons of superconductors C-15 V2Zr and V2(Zr0.5 Hf0.5)". This means that for these superconductors the elastic softening plays a role in enhancing Tc to some extent. It seems that between V2Zr or V2Hf and V2(Zr0.5 Hf0.5) there exists essential difference, which makes Tc increasing and the phonon frequencies softening for the formers while Tc decreasing and the phonon frequencies slightly hardening for the later after adding small amounts of Nb or Ta. It can be considered as the result of hybridzation of conduction bands, which is studied by means of the LMTO (linear combination of muffin-tin orbitals)method.
1985, 34 (12): 1658-1664. doi: 10.7498/aps.34.1658
The Darboux transformation and a new integral transformation are used to transform the schr?dinger-type equation with the P?schl-Teller potential and the modified P?schl-Teller potential. Two classes of exactly solvable double-well potential models are obtained.