Beschreibung
v. Formation of negative ions by processes other than attachment in the gaseous phase at low X/po 17. Introduction. As early as 1912, J. J. THOMSON [32J in his first mass spectro graph observed negative ions of 0-, Cl-, H- and what he believed to be N-. He at first ascribed these to possible dissociation of polar gaseous compounds by electron impact but control studies using ionization at low energies in glow discharges indicated that this was not the origin. O. W. RICHARDSON [33J in his book on emission of electricity from hot bodies reported negative ions to come from hot salts. From there on many experimental studies over the years indicated that negative ions could be formed by various processes. By the middle nineteen hundred and thirties the data fairly clearly identified several processes as being active and MASSEY and SMITH [34J developed the theory underlying some of them. More data are summarized in MASSEY'S excellent little monograph on Negative Ions and in )L\SSEY and BURHOP'S recent book [35]. Since that period, stimulated by various investigations and certain industrial problems, very careful studies of the appearance of such ions by mass spectrograph have been carried out in the laboratory of K. G. EMELEUS in Belfast by SLOANE and his co-workers [3J that haw clarified the questions and indicated what ions have been observed and something of the processes at work.
Inhaltsverzeichnis
InhaltsangabeThermionic Emission.- A. Scope and objectives.- B. Historical highlights.- I. General background.- II. Experiments with clean surfaces.- III. Experiments with composite surfaces (mainly the discoveries).- C. Theory.- I. Statistical mechanics as a basis for emission equations.- II. The density of an electron atmosphere in an enclosed space.- III. Field effects with current flow.- IV. Langmuir's space-charge theory.- V. Idealized use of space-charge method for cathode property determination.- a) Emitter evaluation by accelerating potential methods.- b) Emitter evaluation by retarding potential methods.- c) Emitter evaluation by a combination of retarding and accelerating potential methods.- VI. General theory.- D. Applications of theory to experiments on thermionic emission.- I. General discussion.- II. Emission from single crystals.- III. Modification of electron affinity by polar layers.- IV. The oxide-coated cathode.- Tables.- Appendix 1: Thermionic constants.- Appendix 2: Some useful equations from statistical theory of free electrons.- Field Emission.- I. Introduction.- II. Theory of field emission.- III. Experimental results.- IV. Field emission microscopy.- V. Field emission of positive ions.- References.- Sekundärelektronen-Emission fester Körper bei Bestrahlung mit Elektronen.- A. Einführung.- B. Energieverteilung der Sekundärelektronen.- C. Die Anzahl der Sekundärelektronen (Ausbeute).- D. Weitere Eigenschaften von Sekundärelektronen.- E. Daten über die Bewegung langsamer Elektronen in festen Körpern.- F. Theoretische Ansätze zur Deutung der Sekundäremission.- Literatur.- Photoionization in gases and photoelectric emission from solids.- A. Photoionization in gases.- I. Historical survey.- II. Experimental methods.- III. Experimental cross sections of photoabsorption and photoionization.- B. Photoelectric emission from solids.- I. A survey of photoelectric phenomena.- II. Selected topics on complex surfaces.- References.- Motions of Ions and Electrons.- I. Electron and ion orbits.- a) Orbits in uniform fields.- b) Orbits in inhomogeneous magnetic fields.- c) Pressure gradients.- II. The Langevin equation.- a) Drift.- b) Diffusion.- c) Energy and gain.- III. The Boltzmann equation.- a) The derivative terms.- b) The collision integral.- c) Motions of electrons.- d) The energy distribution.- e) Direct current.- IV. Boltzmann transport equation.- a) General theory.- b) Constant mean free time.- c) Constant mean free path.- d) Polarizable molecules.- V. The Fokker-Planck equation.- a) Flow in velocity space.- b) Rutherford scattering.- c) Maxwellian distribution of scatterers.- d) Stochastic processes.- General references.- Formation of Negative Ions.- I. Fundamentals.- II. Methods of evaluation of h and qa.- III. Measurement of energy of ion formation.- IV. Experimental results and interpretation.- V. Formation of negative ions by processes other than attachment in the gaseous phase at low X/p.- References.- The Recombination of Ions.- I. Basic relations.- II. The measurement of the coefficient.- III. Experimental results and the theories of the recombination coefficient.- References.- Ionization in Gases by Electrons in Electric Fields.- A. Introduction.- I. Historical notes.- II. Collisions between electrons, ions, quanta and atoms.- III. The problem.- B. Ionization in uniform electric fields.- I. The electron multiplication.- II. The electron avalanche.- III. The classical theory of ionization by collision.- IV. The methods of measuring ionization coefficients.- V. The results of the measurements.- a) The observed multiplication.- b) The ionization coefficients.- VI. Collision theory and ionization coefficient.- a) Elementary theories.- b) Comparison of the elementary theory with experiment.- c) Theory of the ionization coefficient in monatomic gases.- VII. Multiplication in the presence of negative ions.- VIII. Multiplication in the presence of positive ions.- IX. Multiplication by metastable atoms colliding with traces
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