ISSN:0021-8979    

DOI:10.1063/1.1722664

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A number of observations have been made of structure changes that occur in hollow and solid electron beams which are confined by a magnetic field. These structure changes occur in both the density of the beam and the transverse velocity components of the beam electrons. The velocity components have been measured by use of a pinhole camera.Some of the results obtained are as follows. The density of electron paths in a beam may become non‐uniform if there is a spread in the forward component of velocity of the electrons. This may occur either because of a spread in initial angle of the electrons or because of a potential depression in the beam.In addition, changes in beam shape and transverse velocity components of the beam electrons can occur as a result of drifting of electrons in crossed electric and magnetic fields, the electric fields in this case being provided by the space charge of the electrons themselves. Thin beams have been found to be unstable and it has been observed that they divide into an array of vortex‐like current filaments when the beam current is sufficiently high. A possible connection between this occurrence and phenomena in the aurora is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1722665

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Investigations of Schottky emission from metals, including some recent work, are summarized and discussed. The following are some of the conclusions: The surface barrier outside a uniform metal surface can be represented accurately by a mirror‐image form for distances greater than about 20 A from the surface. Patch effects can be correlated to some extent with known surface properties. The dependence of photoelectric emission on applied field is in agreement with the Fowler theory adjusted for a Schottky‐type field‐dependent threshold. Periodic deviations from the thermionic Schottky effect are in full agreement with the mirror‐image model for the extra‐surface barrier, and can be used in determining the barrier form in the immediate vicinity of the emitter surface.

ISSN:0021-8979    

DOI:10.1063/1.1722666

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

This paper is a review of recent developments in the theory of electron emission from metals. The main subjects discussed are the periodic deviations in the Schottky effect and the transition between thermionic and field emission. The indications are that each of these phenomena can be understood in terms of the free electron model for the metal and the transmission of the electrons through the image force barrier at the metal surface.

ISSN:0021-8979    

DOI:10.1063/1.1722667

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

It is claimed that the poor agreement often found between the energy quantities measured by mass spectrometry, and those obtained by other methods, is due in large part to the interpretation of the experimental data. The conditions necessary for accurate measurement are summarized.It is shown that by making certain assumptions about the probability of ionization for different processes, ionization efficiency curves can be interpreted to give the probabilities for electronic transitions from the ground state to the various ionic states of molecules. From these electronic transition probabilities, information can be deduced about the potential energy functions for these upper states.To exploit the method fully, beams of ionizing particles with low spreads in energy are necessary. Electron and photon impact are compared, and it is shown that the latter possesses many advantages.

ISSN:0021-8979    

DOI:10.1063/1.1722668

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Experiments on the formation of negative ions by electron bombardment of hydrogen, oxygen, and water vapor at pressures of 0–4 mm are described. The only ion observed in hydrogen is H−, formed by dissociative attachment. Pressure dependence of the O2−intensity shows that a secondary collision is involved in its formation. Data on the formation of O−and O2−at low electron energies indicate that the secondary collision leading to the formation of O2−does not involve an O−ion. The formation of O2−probably involves a stabilizing collision with a molecule of gas after the initial formation of the ion by electron attachment. From the behavior of H−, O−, and OH−intensities with H2O pressure, it is shown that the secondary process for the formation of OH−in water vapor is probablyH−+H2O→OH−+H2.The cross section for this reaction is more than 10−17cm2.

ISSN:0021-8979    

DOI:10.1063/1.1722669

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The etching behavior of as‐grown and heat‐treated silicon crystals has been studied using an etching procedure developed by Dash. The rate of chemical etching of silicon was found to decrease with increased concentration of dissolved oxygen. This effect impedes the formation of etch‐pits. To explain the observed etching behavior after heat treatment it is necessary to assume that the rate of chemical etching increases with increased amount of precipitated oxygen in pulled crystals.

ISSN:0021-8979    

DOI:10.1063/1.1722670

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Lifetime data of 46 pulled silicon crystals are interpreted in terms of the Shockley‐Read recombination theory. The data are consistent with the theory under the assumption of a single recombination level and a constant concentration of recombination centers, independent of the resistivity of the crystals. However, it is not possible to distinguish between two possibilities as to the location of the recombination level in the lower or the upper half of the energy gap by this type of experiment.The energy levels thus obtained are at 0.17 ev from the valence band or 0.20 ev from the conduction band inp‐type silicon and at 0.22 ev from the valence band or 0.25 ev from the conduction band inn‐type silicon.

ISSN:0021-8979    

DOI:10.1063/1.1722671

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Studies have been made of the process in which donors are introduced into silicon by heating in the temperature range 300°–500°C and are caused to disappear on heating at higher temperature. This phenomena is shown to depend on the conditions of growth and the heat‐treatment history of the crystal. Evidence is summarized which shows that oxygen is the impurity from which the donors are formed. The characteristics of the processes involved are described and possible mechanisms are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722672

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The explosive production of plane shock waves in solids is analyzed in the approximation that third and higher order terms in the shock strength can be neglected, and a procedure is developed for calculating the attenutation of the shocks. Application is made to the problem of determining the equation of state of the burned explosive gas.

ISSN:0021-8979    

DOI:10.1063/1.1722673

出版商:AIP    

年代:1957

数据来源: AIP