摘要:

Analytic solutions for the shear stress and energy factors of three basic types of edge dislocations in cubic anisotropic crystals have been published previously based on the general solution of Eshelby, Read, and Shockley. Naming the slip plane and Burgers vector in order, the dislocation types referred to are {010}, ⟨100⟩; {1¯10}, ½⟨110⟩; and {001}, ½⟨1¯10⟩. The most important kind of edge dislocation in fcc metals and diamond‐type crystals, however, is of type {111}, ½⟨11¯0⟩, belonging to by far the most important slip system. This problem has previously been considered by Seeger and Scho¨ck. In the present paper, analytic solutions are derived for the shear stresses and energy factors of the {111}, ½⟨11¯0⟩ edge dislocation and are evaluated numerically for the cases of aluminum, &agr;‐brass, copper, gold, lead, nickel, silver, thorium, diamond, germanium, and silicon. The results are compared to those obtained from isotropic elasticity theory and an approximation introduced by Aerts, Delavignette, Siems, and Amelinckx.

ISSN:0021-8979    

DOI:10.1063/1.1708973

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The condition for frequency locking of a laser oscillator by an externally injected signal is derived. The results allow one to estimate the minimum‐frequency separation in rotation sensing ring lasers as a function of scattering in the beam path. The formula may also be used as a design criterion in phase‐locking arrays of laser oscillators.

ISSN:0021-8979    

DOI:10.1063/1.1708974

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The coupling of uniaxial ferromagnets whose easy directions are not parallel is studied. It is shown that field‐dependent effective high‐order anisotropies may be produced, and that as the coupling is weakened increasingly high‐order anisotropies will become detectable. These results are applied to uniaxial thin films with anisotropy dispersion. It is shown that treating such films as having complex uniaxial and biaxial anisotropy is somewhat oversimplified.

ISSN:0021-8979    

DOI:10.1063/1.1708975

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The pulses due to electron avalanches released in dry air from a cathode of a uniform field gap (6 cm) by photoelectrons in a time interval of about 40 nsec are investigated. Using a new method of evaluation which yields simpler formulas, the attachment coefficient &eegr; for formation of unstable negative ions and the mean lifetime &tgr; of these ions are determined. In the pressure range 4–60 Torr, &eegr;/pis independent of pressure and increases in theE/prange 33–53 V cm−1Torr−1from 0.006 cm−1Torr−1to 0.017 cm−1Torr−1. In the same pressure range, &tgr;pis independent of pressure and decreases from 35 &mgr;sec Torr to about 2 &mgr;sec Torr.Our results confirm the earlier assumption of one prevailing kind of unstable negative ion. The value of &eegr;/pagrees with that obtained earlier atE/pclose to 40 V cm−1Torr−1. A distinct variation of &eegr;/pwithE/p, not reported earlier, is obtained.

ISSN:0021-8979    

DOI:10.1063/1.1708976

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The gases desorbed when a tungsten target in vacuum of the order of 10−8Torr is struck by a Q‐switched laser beam are studied. The apparatus used in the experiment is described. The data presented are for water vapor, carbon monoxide, and carbon dioxide. Analysis is presented to demonstrate that the data are compatible with a model in which the laser is considered to be no more than a pulsed heat source for laser energy densities up to 50 MW/cm2.

ISSN:0021-8979    

DOI:10.1063/1.1708977

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Electron spin resonance (ESR) was studied in five semiconducting diamonds in the temperature range 108°–370°K and at 4.2°K. Thegfactor is 2.0030±0.0003, and the linewidth varies from 0.3 to 8 Oe at room temperature. The number of spins contributing to the ESR absorption varies between 1013–1014and agrees with the number of uncompensated acceptors in the case of two diamonds on which Hall and resistivity measurements were made. The number of spins varies as 1/Tin the temperature range 108°–370°K. The spin‐lattice relaxation time was estimated to be of the order of 10−8sec at 300°K. The results indicate that the spin center is associated with the acceptors in thep‐type diamonds. The effect of heat treatment on the ESR absorption (g=2.0029) observed in crushed nonconducting diamond was measured. The intensity and linewidth (2.9 Oe) for the crushed diamond was reduced on heating at 600°C; further heating at 1100°C did not change the ESR line after the initial decrease.

ISSN:0021-8979    

DOI:10.1063/1.1708978

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The energy distributions of positive ions ejected from polycrystalline Mo and Ni by He+, Ne+, and Ar+primary ions in the energy range of 0.5 to 3.0 keV have been found to consist of a low‐energy distribution characteristic of sputtered ions and a sharp peak at higher energy. These high‐energy ions are shown to be primary ions which have experienced single two‐body collisions with the surface atoms. Multiply‐charged ions were not detected. It was found that, approximately, a monolayer of adsorbed gas was sufficient to prevent the detection of incident ions which have scattered from the metal target atoms. He+primary ions have been used to identify CO as an adsorbed gas on the Ni surface. Furthermore, the data suggest that the CO molecule forms a linear bond with the Ni surface through the C atom, as has been previously observed by other techniques. In contrast, when more reactive gas ions were used as primaries, nonsharp or continuous scattered ion energy distributions were observed, suggesting that lower neutralization probabilities associated with these ions allow the detection of ions which have penetrated deeply into the surface and emerged with varying energy losses.

ISSN:0021-8979    

DOI:10.1063/1.1708979

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The linear compression of &agr;‐quartz relative to NaCl has been determined by x‐ray diffraction methods. The data agree within experimental error with an extrapolation formula derived by Thurston in which the parameters are the elastic constants and their first‐pressure derivatives. This is an extrapolation of two orders of magnitude. A high‐pressure Guinier‐type focusing x‐ray camera is described and the problem of pressure calibration is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1708980

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A combination of capacitance,I‐V, and photoresponse data is presented for metal‐semiconductor junctions on KTaO3. Results are in good agreement with the Schottky theory for doping levels below 1018cm−3. Substantial deviations occur for higher doped samples. Measured barrier potentials do not correlate with either the metal work function or the metal electronegativity, and appear to be strongly affected by strains at the metal‐semiconductor interface. In the case of Cu and Au, structure in the photoresponse data associated with an energy‐dependent density‐of‐states is observed.

ISSN:0021-8979    

DOI:10.1063/1.1708981

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A series of experiments is described showing parametric amplification of traveling magnetoelastic waves in single‐crystal YIG in the frequency range 1–10 GHz. The process involves a pump field at right angles to the dc field, with almost exactly twice the signal frequency. Pulse echo techniques were used to observe amplified echoes in both axially and transversely magnetized rods and in normally magnetized disks. The time delay of the echo is a function of applied magnetic field strength and amplification is observed only if the pump is provided at a particular time. The amplification in a rod is largest when the field is directed ≈15° off the rod axis and in this case the pump must be applied approximately when the signal is in the magnetoelastic crossover region. A net gain exceeding 55 dB was obtained at 1.5°K for X‐band signals with 10‐&mgr;sec delay. At room temperature, 6‐dB net gain was obtained in X‐band at 3‐&mgr;sec delay with 250 W of pump power, and 17‐dB net gain was obtained in L band with only 0.6 W of pump power. The observed echo behavior indicates that the transverse pumping process involves a pair of shear magnetoelastic waves on the same branch of the dispersion curve and occurs near the magnetoelastic crossover point. The theoretical instability thresholds are derived for several processes involving transversely pumped, magnetoelastic shear waves, but the results do not agree with the most direct explanation of the experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.1708983

出版商:AIP    

年代:1967

数据来源: AIP