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Vol. 20, No. 11 (1964)

1964-06-05
CONTENT
THE SPIN-WAVE SPECTRUM AND ITS EXCITATION IN A FINITE FERROMAGNETIC-ANTIFERROMAGNETIC LINEAR CHAIN
WANG DING-SHENG, PU FU-CHO
1964, 104 (11): 1067-1078. doi: 10.7498/aps.20.1067
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The system of spins in a finite ferromagnetic-antiferromagnetic chain, coupled by exchange interaction, is investigated. The spin-wave spectrum and the intensities of its excitation are calculated. On the basis of the results obtained, the spin-wave resonance of a ferromagnetic film with a surface of antiferromagnetic oxide is discussed. The validity of the general phenomenological boundary condition is elucidated. The value estimated for the equivalent surface anisotropy energy according to our theory is found to be in fairly good agreement with experimental data.
ON THE LINEWIDTH OF LASERS
FANG LI-ZHI, LUO YI-ZU
1964, 104 (11): 1079-1089. doi: 10.7498/aps.20.1079
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In this paper, the "short-time" part of the linewidth of a laser beam has been considered with the fundamental equations which describe the behaviours of lasers. This linewidth is described usually by △vs=(8πhv(△v′)2)/P, (1) here △v′ is the half-width of the electromagnetic mode of cavity, v the beam frequency, and P the output power. The main results can be summarized in the following way: (1) The linewidth is raised mainly from the dissipative system coupled to the electromagnetic mode, and the contribution of the dissipative system coupled to the molecules is negligible. (2) In the single-mode approximation formula (1) is correct, only if 1/T2?1/(2π)△v′,1/T2 being the homogeneous linewidth of molecules. (3) If the inter-actions between the exciting mode and other modes in the multimode cavity are strong, then formula (1) will be generalized to the following: △vs=(8πhv(△v′)2)/P+(4hv(△v′))/P somefromn=(λ′≠λ)(rλλ′2/(rλ′),(2) here γλλ′ is the correlative relaxation coefficient and γλ′ is the half-width of mode λ′. In certain case the second term in formula (2) may be much larger than its first term. Therefore, it is one of reasons for the disagreement between the experimental results about the linewidth and the prediction from formula (1).
INELASTIC AMPLITUDES IN THE LEE MODEL POSSESSING CROSSING SYMMETRIES
T. S. CHANG
1964, 104 (11): 1090-1100. doi: 10.7498/aps.20.1090
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The first inelastic amplitudes in the Lee model possessing crossing symmetries are shown to satisfy a pair of simultaneous integral equations of Omne's type which may be solved in the usual way, on assuming known elastic amplitudes. The equations may be written in such a way that the inhomogeneous terms are small in the elastic region of one of the variables. From this, it is shown that it is possible that the inelastic contributions to the absorptive part of the elastic scattering are small in the first inelastic region.A set of integral equations displaying fuller crossing symmetry among the θ particles involved is proposed.
THE LIFETIME OF THE MUON AND THE EXPERIMENTAL LIMITATION OF THE μ-e SYMMETRY
LU TAN, LO LEAU-FU, YANG KUO-SHEN
1964, 104 (11): 1101-1113. doi: 10.7498/aps.20.1101
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The μ-e symmetry is destroyed by the anomalous interaction. We discuss the influence of the anomalous interaction on the weak-processes, and analyse the relation between the renormalization of the weak-interaction constant and such properties of the anomalous interaction as the charge independence and the γ5-transformation. The re-normalized constants are shown to be GV=G,GA=εG,ε=1+δ. This result is used to solve the difficulty which occurs when one uses the universal V-A Fermi weak-interaction theory and the conserved vector current hypothesis to explain the lifetime of the muon. Comparing the thory with various experiments, we obtain δ = 0.04, which may be interpreted as the experimental limitation of the μ-e symmetry.
A GENERALIZED EFFECTIVE SPIN-HAMILTONIAN
LIN FU-CHENG, HUANG WU-HAN, ZHU JI-KANG
1964, 104 (11): 1114-1123. doi: 10.7498/aps.20.1114
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A generalized effective spin-Hamiltonian HSG describing the EPR of transition group ions in crystal is proposed on the basis of group theory. In this method, HSG is considered strictly by the space-time symmetry. In the first order perturbation, the irreducible spin tensors TLM (L=0,1,…, 2S) describe completely the EPR of paramagnetic ions with ground state having (2S + 1) energy levels. Irreducible tensors in several point-group symmetries are presented for convenience of obtaining HSG explicitly. Such a HSG is equivalent to the Koster-Statz matrix.
ON TRANSIENT PROCESSES IN PLASMA
LOH CHYUAN-KONG
1964, 104 (11): 1124-1128. doi: 10.7498/aps.20.1124
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In this paper, we investigate the macroscopic transient properties in plasma caused by a pressure gradient perpendicular to a constant magnetic field. Under the condition of zero initial flow velocity normal to the magnetic field, we get the instantaneous diffusion coefficient (when ωceτ?1) D= (2kmec2)/e2 T/(B2τ)+(kc)/eT/Be-(me t)/(mi τ)sinωcit, where τ is the mean collision time between an ion and an electron.
K-K RESONANCE
HSU PEI-WEI, KUNG FAN-MEI, KUNG HSUCH-HUI
1964, 104 (11): 1129-1134. doi: 10.7498/aps.20.1129
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The existence of a resonance in K-K pair with a mass of 1.02 BeV has been recently observed in π--p and K--p collisions. In several reports the quantum numbers in this resonant state have been determined, but the results are different from one another. From the field theoretical point of view and by means of the chain approximation, we have calculated the interaction potential of K-K system and indicated that there is a resonance in 1.02 BeV T=0,JPG=0++.
INTERNAL FRICTION DUE TO DISLOCATIONS IN MOLYBDENUM AT KILOCYCLE FREQUENCY
WANG YEH-NING, TING SUI-DIN, JIANG SHOU-SHENG, WANG SHIH-YUAN
1964, 104 (11): 1142-1152. doi: 10.7498/aps.20.1142
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Internal friction as a function of strain amplitude in zone-refined molybdenum single crystals and commercially pure polycrystalline molybdenum was measured with the three-component piezo-electric resonator method developed by Marx. A Granato-Lücke (GL) type of strain-amplitude-dependent decrement was obtained in molybdenum single crystal annealed in hydrogen at 2000℃. With some prior deformation in molybdenum single crystal, a plateau (or maximum) appears on the decrement-amplitude curve, which is similar to the results of pure aluminium at low temperature and low strain amplitude. From the observations of dislocation etch-pits, it may be concluded that the presence of this plateau is related to the fresh dislocations (or weakly pinned dislocations) produced by cold work. The increase of decrement at the plateau (or maximum) is proportional to the density of fresh dislocations. The investigations of the effects of temperature and aging (200-300℃) on the amplitude-dependent decrement indicated that the decrement decreases with the decrease of temperature and with the increase of aging time, and the position of the maximum shifts to the higher amplitude as the temperature decreases. All the results are discussed in terms of an extension of the GL theory.The effect of cold work on the strain-amplitude-dependent decrement of poly-cryctalline molybdenum was also measured; the results are fairly consistent with the GL theory.
GE IR INTERFEREMETER
T. F. HU, C. WEI, C. S. CHANG
1964, 104 (11): 1164-1171. doi: 10.7498/aps.20.1164
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A germanium interferometer which may be used for measuring the dispersion curves of organic liquids in the spectral region of 2-11 microns is described. It was found that the dispersion curves of benzene and chloroform in the 2-6 microns region measured with this interferometer are in good agreement with those obtained by other authors.
BRIEF REPORT
1964, 104 (11): 1172-1175. doi: 10.7498/aps.20.1172
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1964, 104 (11): 1176-1177. doi: 10.7498/aps.20.1176
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1964, 104 (11): 1178-1179. doi: 10.7498/aps.20.1178
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1964, 104 (11): 1180-1181. doi: 10.7498/aps.20.1180
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1964, 104 (11): 1182-1186. doi: 10.7498/aps.20.1182
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