摘要:

Striations, with an average lifetime of about 5 &mgr;sec, have been observed during the initial phase of electrical breakdown in H2, at pressures ranging from 3 to 50 Torr, and with 2.5 kV applied across a 5‐mm gap. The striations were observed to propagate towards the cathode at about 104cm/sec, but the rate of advance of the appearance point of the striations was at least four times faster and towards the anode.

ISSN:0021-8979    

DOI:10.1063/1.1703077

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

We have investigated theoretically and experimentally the conditions under which spiking in the laser output can be completely suppressed. It is predicted that a nonlinear absorber in the cavity producing greater loss at the higher power levels, and vice versa, should be highly effective. Experimental work was carried out with a single‐mode traveling‐wave laser, since in this case the predictions can be most easily checked. Instead of using a nonlinear absorber, a Kerr cell controlled by a feedback circuit was used. It was found, in agreement with theory, that the time delay between the build‐up of the electromagnetic energy in the cavity and the corrective action of the Kerr cell is a rather important parameter. Spike suppression can only be obtained when this time delay is short as compared to the duration of one oscillation pulse.

ISSN:0021-8979    

DOI:10.1063/1.1703078

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements have been made of the primary and secondary electron ionization coefficients in neon‐hydrogen, helium‐hydrogen, and neon‐argon mixtures using the Townsend technique. In these experiments, measurements have been conducted over a considerable range of pressures at theE/p0value corresponding to the maximum of the Penning effect and for the optimum concentrations. Examination of the prebreakdown current growth indicated at fixedE/p0a pressure‐dependent breakdown potential. Measurements of the primary coefficient as a function of pressure showed no significant pressure variation. Measurements of the secondary ionization coefficient, however, indicated that &ggr; decreased with increasing pressure consistent with the observed breakdown potential variation.

ISSN:0021-8979    

DOI:10.1063/1.1703079

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

We have measured the induced thermionic emission of electrons from tantalum as the result of bombardment with laser beams of up to 105‐W/cm2peak power density as a function of the tantalum temperature. It is shown that within the power range investigated, the results can be described in detail as thermionic emission resulting from a temperature increase which is calculable from classical heat‐transfer theory.

ISSN:0021-8979    

DOI:10.1063/1.1703080

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The frequency and polarization dependence on applied stress of the output radiation of PbTe and PbSe diode lasers is discussed. Because the energy gap decreases with applied pressure, the output wavelength can be tuned over a wide range. It is estimated that the emission from a PbSe diode can be tuned continuously from its unstressed value of 8.5 &mgr; by a 100 uniaxial stress to 9.6 &mgr; at 5×103atm and to 10.5 &mgr; at 104atm. It is proposed that sound waves can be used to frequency‐modulate a laser diode.

ISSN:0021-8979    

DOI:10.1063/1.1703081

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A number of emission bands lying several tenths of an eV below the band gap have been observed in photoluminescence spectra of GaP crystals. These bands shift in peak position as different donors and acceptors are incorporated in the crystals. The emission bands are identified as donor‐acceptor pair recombination bands involving deep levels by noting that these shifts correspond directly to changes in the donor and acceptor binding energies and by noting their similarity to shallow donor‐acceptor pair bands previously identified as such. One of these bands is due to recombination between the deep donor oxygen and the shallow acceptor zinc. Inp‐type crystals thermal ionization of minority carriers trapped on the deep donor is small, so that in samples containing optimum concentrations of zinc and oxygen, photoluminescence (external) quantum efficiencies as high as 1.5% have been measured at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1703082

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Silicon is bombarded at 400° to 900°C in a glow discharge of hydrogen with phosphine or diborane admixtures. Below 700°C, bombardment ofn‐type silicon with an initial resistivity of 200 &OHgr;‐cm creates deep (0.5–2.5&mgr;)p‐type surface layers regardless of gas composition. The concentrationNA(x) of the acceptors in theplayers obeys a simple law:NA(x)=N0exp(−x/L).N0is the surface concentration atx=0 which increases from 3.5×1016acceptors cm−3to 4×1018acceptors cm−3for bombardment temperatures increasing from 500° to 650°C. The decay constantLis found to be 0.2 &mgr;. Annealing experiments rule out the hypothesis that theplayers are caused by fast‐diffusing acceptor impurities, e.g. aluminum or boron. It is proposed that theplayers are formed by vacancies which act as acceptor‐like defects.

ISSN:0021-8979    

DOI:10.1063/1.1703083

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Measurements have been completed of electron‐density relaxation in cesium‐seeded plasmas perturbed from thermal equilibrium at temperatures in the 1500° to 2000°K range. The gases consisted of 0.1 to 20 Torr Cs vapor in atmospheric pressure argon or helium. Electron densities ranged over 1.9×1011to 3.8×1013cm−3and relaxation times over 30×10−6to 50×10−3sec. The results indicate that charge production and loss are dominated by the atomic‐ion process Cs+e+3.89 eV↔Cs++2eat the higher temperatures, and by the molecular‐ion process Cs+Cs+2.82 eV↔Cs2++eat the lower temperatures and higher cesium pressures. At the lower temperatures and lower cesium pressures the dominant process is ambipolar diffusion. The results obtained when the atomic‐ion process dominates agree well with calculations based on the equilibrium properties of the gas and recent theory for two‐electron, three‐body recombination. The rate of the molecular‐ion process corresponds to a two‐body recombination coefficient of approximately 1×10−8cm3/sec at temperatures of 1250° to 1400°C, a value small relative to that derived from earlier experiments. All evidence indicates that, despite their numerical preponderance, the argon and helium atoms play no significant roles beyond those of thermal bath and diffusion barrier.

ISSN:0021-8979    

DOI:10.1063/1.1703084

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A method is presented for the analysis of relaxation spectra resulting from Maxwell‐Wagner interfacial polarization in sintered oxide compacts. Using a multilayer model to represent ferric oxide pellets, containing heterogeneities induced by the sintering process, a distribution function of the relaxation times is derived which, when applied to the Maxwell‐Wagner equation for a simple two‐layer capacitor, gives an equation empirically found to describe the dielectric properties of the samples. Data are presented to show the close parallel between the distribution of relaxation times, predicted by the distribution function, and the distribution of resistivities found to be present in the samples from dc measurements. Comparisons are made between the data predicted by the analytical equations and those obtained from experimental methods. It is concluded that the use of a distribution function of the relaxation times for the analysis of the relaxation spectra is physically justifiable and that the multilayer model in conjunction with an asymmetric distribution function is capable of accurately describing the relaxation spectra observed in sintered compacts of &agr;‐Fe2O3.

ISSN:0021-8979    

DOI:10.1063/1.1703085

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The effect of Hg adsorption on atom ejection patterns in Hg+ion bombardment of Ni low‐index planes has been studied. The atom ejection patterns observed for single‐crystal sputtering become smeared out when a Hg film is adsorbed on the target surface. The transition is unusually sharp and is interpreted to be the result of a two‐dimensional condensation. A heat of adsorption of 0.69 eV/atom is derived from the model. The sputtering rate of the adsorbed Hg film seems to be determined more by the substrate than by the surface atom binding energy.

ISSN:0021-8979    

DOI:10.1063/1.1703086

出版商:AIP    

年代:1965

数据来源: AIP