Vol. 21, No. 5 (1965)
1965-03-05
CONTENT
1965, 21 (5): 889-896.
doi: 10.7498/aps.21.889
Abstract +
In this paper, a persistent-current method for measuring critical characteristic curves of superconductors has been described. In comparison with the usual four-probe method, this new method possesses the following advantages: (1) The Ic (H) curves thus determined have clear physical significance. (2) The technical difficulty of introducing heavy current into the cryostat is avoided. (3) There is no danger of burn-out of the specimen tested.The Ic(H) curve of cold worked niobium wire has been determined with this method. The result confirms the existence of the peak in the Ic (H) characteristic observed previously with the four-probe method.
1965, 21 (5): 897-906.
doi: 10.7498/aps.21.897
Abstract +
The even parity states of O16 are treated by taking into account the configuration of 2 ?ω excitation in the L-S coupling scheme and using the δ-interaction of the Wigner type. An approximate method is suggested and the 0+, 2+, 4+, states are solved. Rigorous solutions of the wave functions are obtained as well and compared with the approximate solutions. It is found that they are very close to each other. By using these approximate wave functions the monopole and E2 transition probabilities are calculated, and the results are in nice agreement with experiment, but do not show agreement for the energy level spacings.
1965, 21 (5): 915-951.
doi: 10.7498/aps.21.915
Abstract +
By making use of the method for treating the pairing force, which conserves the number of particles, we have analysed the influences of pairing force on the various properties of actinide nuclei, including the intrinsic spectra of odd-A nuclei and even-even nuclei, β-decays and α-decays, etc. The general formula expressing the influences of pairing force on the various types of α-decay, are given.1. First, Nilsson's parameters, which, after the pairing force being taken into account, can account for the observed intrinsic spectra of odd-A nuclei, are determined. It is found that they may be chosen as follows: K～0.050, η～4.4-5.4 (δ～kη)～0.22-0.27) μ～ 0.70(N = 5), μ～ 0.62-0.66(N = 6), for protons, μ～0.43-0.45(N = 6), μ～0.41-0.43(N = 7), for neutrons. 2. Subsequently, with such realistic single-particle spectra, the intrinsic spectra and β-decays of neighbouring even-even nuclei (Th228,Th230,U232,U234, Cm244) are analysed in detail. Some observed levels (E≥1 MeV.) may be explained as the pair-broken states or the pair-excitation states. (See Table 14, and Figs. 15, 16.) According to calculation, there exist still many levels in the energy region, E～l-2 MeV, but they have not been observed yet. In the β-decay experiments, the majority of these levels can not be detected easily, but some of them, easily. The systematically occurring vibrational bands in the spectra of even-even nuclei could not be considered as the pair-broken states or the pair-excitation states. They areγ-vibrational states, Kπ=2+, E～0.8-1.0 MeV;β-vibrational states, Kπ=0+, E～0.7-0.9 MeV;octupole b-vibrational states, Kπ=0-, E～0.5-0.7 MeV. 3. The influences of pairing force on the α-decay probabilities are treated both with the BCS method and with the present method. The results, especially for the favoured a-decay, are quite different in the two methods. For example, when about 10 levels are involved, the retardation factors for the favoured α-decay of even-even nuclei are:R = RZRN≈200 (BCS wave function), R = RZRN ≈ 70 (exact solution). Compared with the exact solution, the occupation probability of the v-th levels, vv2, in the BCS method converges too slowly. In the BCS wave function, the portion, in which the number of particles is equal to the average number of particles, is about one third. After the influence of pairing force is taken into account, the nuclear radius constant derived from the a-decay is about r0～1.35fm. The favoured a-decay of odd-A nuclei and the unfavoured a-decay are also discussed. The so-called F-factors are calculated and compared with experiments.
1965, 21 (5): 952-960.
doi: 10.7498/aps.21.952
Abstract +
By using the Bohr-Mottelson model, and taking the vibration-rotation interaction into account more carefully, the energy spectra and the rates of electric quadrupole transitions of even-even nuclei in the transition region can be well explained.
1965, 21 (5): 976-982.
doi: 10.7498/aps.21.976
Abstract +
A cloud chamber experiment is described, in which the angular distribution of secondary particles produced in nuclear interaction by high energy cosmic ray particles with paraffin has been studied. Sixty-four ns≥4 events with average primary energy of 70 BeV have been analysed. The result shows that, in this energy region, the angular distribution in CMS is not isotropic but possesses maxima in the 0° and 180° directions; furthermore, there is already an appreciable fraction (≥20%) of the events with angular distribution exhibiting the features given by the "fire-ball" model.
1965, 21 (5): 983-988.
doi: 10.7498/aps.21.983
Abstract +
It is proved that for the highly singular potential satisfying the conditions expressed in a previous paper [1] the S matrix element S (λ, k) has the representation.
1965, 21 (5): 989-996.
doi: 10.7498/aps.21.989
Abstract +
The orientations of NiO formed on evaporated Ni single-crystal films with surfaces parallel to (110), (001), or (111) have been studied by means of electron diffraction. Beside that the parallel orientation relationship already known to exist between NiO and Ni has been confirmed, the following NiO textures have been found in the present investigation: texture: (111)NiO// (001)Ni, NiO// Ni; fibre texture: NiO//Ni. It was shown that NiO//(110>Ni is common to all orientation relationships between NiO and Ni, thus making it clear that the close-packed direction plays an important role in the epitaxial growth of f.c.c. crystals. The various trends of epitaxial growth of NiO are discussed with respect to the number of directions on the film surface and to the degree of perfection of Ni films.
1965, 21 (5): 997-1007.
doi: 10.7498/aps.21.997
Abstract +
The crystal structure of V2Ga5 has been determined by the method of X-ray diffraction from single crystal oscillation photographs and Debye-Scherrer photographs. The homogeneity range of this phase in the V-Ga system extends approximately from VGa2 to V2Ga5. The crystal belongs to the tetragonal system, the lattice spacings at 18℃ being a = 8.9540? and c = 2.6892?. There are two formula units per unit cell. The space group is D4h5-P4/mbm. The four V atoms are situated at the 4(h) positions, while the ten Ga atoms are situated at the 8(i) and 2(d) positions, with xh= 0.180, xi= 0.070, and yi= 0.210.
1965, 21 (5): 1015-1037.
doi: 10.7498/aps.21.1015
Abstract +
The transverse magnetoresistance of n-type germanium materials for both the acoustic and the ionized impurity scattering mechanisms has been inverstigated. In a degenerative case under a strong magnetic field, the expressions of the magnetoresistance of germanium in the three directions of , , and are obtained with respect to the acoustic scattering. The relative magnitude of the average values of theseresults are (ρt)/ρ0:(ρt)/ρ0:(ρt)/ρ0=1:1.7:1.1. In the nondegenerative quantum-limited case, the expressions of the transverse magnetoresistance of germanium for both acoustic and impurity scattering are obtained respectively. For acoustic scattering ρt/ρ0～H/T and, furthermore, ρt/ρ0 is independent of the direction of the magnetic field; for impurity scattering ρt/ρ0～T/H and ρt/ρ0 is dependent on the direction of the magneticfield except for certain specific case.Among the results, the magnetoresistance for the acoustic scattering in a non-degenerative quantum-limited case is qualitatively in accordance with the experimental results given by Diesel and Love.
1965, 21 (5): 1038-1048.
doi: 10.7498/aps.21.1038
Abstract +
The carrier lifetimes of p-type and n-type InSb are measured by the stationary photo-conductive and photoelectromagnetic method in the temperature range 85-290°K. The carrier lifetimes of all intrinsic samples tend to the same value as the temperature increases toward the room temperature. It is 3×l0-8 sec at 290°K. From the absolute value and temperature dependence of the lifetime and the influence of the doping, it is concluded that the carrier lifetime in InSb around the room temperature is controlled by the band to band impact recombination.Below 200°K, the lifetimes of majority and minority carriers in p-type InSb are different in magnitude and temperature dependence. It can well be explained by assuming the existance of a set of electron traps at 0.11 eV below the conduction band in conjunction with a set of recombination centres at 0.05 eV above the valence band.
1965, 21 (5): 1061-1074.
doi: 10.7498/aps.21.1061
Abstract +
The ultrasonic absorption in aqueous suspensions (essentially at low concentrations) has been investigated by the pulse interferometric technique. Epstein's theory on this effect is briefly reviewed with the general expressions as well as those of limiting cases for calculating the sound attenuation coefficients derived and discussed corresponding to the actual experimental conditions.Measurements were conducted in aqueous suspensions of the pollen of pinaceae in the frequency range from 3 to 20 Mc at temperatures 20-80℃ for different concentrations. To reduce the measuring errors to a minimum, methods employing both single and multiple pulses, and comparing the pulse height in two troughs one with and the other without the hydrosols, were alternately adopted. Theoretical values based on rigorous formulae and calculated by aid of the electronic digital computer were compared with the experimental ones.Measuring data and corresponding theoretical interpretations based on approximate formulae from some other authors for aqueous suspensions of lycopodium were critically examined. It was pointed out that some of their agreement was fortuitous. The order of magnitude of absorption due to viscosity and scattering under different experimental conditions for the two suspensions was discussed in some length.
