Emission of Positive Ions Formed at Metal Surfaces (Surface Ionization)

1965 ◽  
pp. 98-135 ◽  
Author(s):  
Manfred Kaminsky
Keyword(s):  
Metal Surfaces ◽  
Surface Ionization ◽  
Positive Ions

The theory of the extraction of electrons from metals by metastable atoms, II

1931 ◽  
Vol 27 (3) ◽  
pp. 460-468 ◽  
Author(s):  
H. S. W. Massey
Keyword(s):  
Hydrogen Atom ◽  
Velocity Distribution ◽  
Spherical Cavity ◽  
Metal Surfaces ◽  
Excited Atoms ◽  
Positive Ions ◽  
Order Of Magnitude ◽  
The Impact

In a previous paper the nature of the phenomena occurring when electrons are ejected from metal surfaces by the impact of metastable atoms and positive ions was discussed. It was shown that electrons may be ejected by excited atoms at considerable distances from the surface, and by considering the case of an excited hydrogen atom at the centre of a spherical cavity in the metal the order of magnitude of the effects to be expected and the velocity distribution of the ejected electrons was determined. In this paper the theory will be extended in two directions.

scholarly journals An investigation of the effects of electron collisions with platinum and with hydrogen, to ascertain whether the production of ionisation from platinum is due to occluded hydrogen

1920 ◽  
Vol 97 (681) ◽  
pp. 23-43 ◽  
Keyword(s):  
Metal Surface ◽  
Metal Surfaces ◽  
Direct Proof ◽  
Ionisation Potential ◽  
Electron Collisions ◽  
Electron Stream ◽  
Positive Ions ◽  
Minimum Velocity ◽  
Positively Charged ◽  
Made In

In the course of an investigation of the effects of electron collisions with helium atoms, it was found that positive ions were produced from a positively charged platinum gauze when this was bombarded by electrons with a minimum velocity of about 11 volts. The production of positive ions in this way does not appear to have been observed before for such small velocities of the impacting electrons, though their detection with primary rays of 30 volts speed is recorded by Campbell in the account of his experiments on ionisation by charged particles. In this paper Campbell gives an excellent summary of the work which has been done in connection with the bombardment of metal surfaces by slow cathode rays. The work of Lenard, Baeyer, Gehrts, Campbell, and others has established the facts that, when such rays fall on a negatively charged metal surface, electrons leave the surface, and that the number and the speed of these electrons depends on the velocity of impact of the primary stream. When the velocity of the incident rays is less than 11 volts, the electrons leaving the plate are those of the primary stream which have been reflected at the metal surface, the characteristic of these reflected rays being that most of them have a velocity comparable with that of the incident rays. When the velocity of impact reaches 11 volts, in addition to reflexion, an excitation of secondary rays begins and gradually increases in amount as the speed is further increased up to about 200 volts. On this account the curve showing the relation between the velocity of impact and the number of electrons leaving the plate takes an upward turn at 11 volts, but no other bend occurs until 200 volts is reached. It has therefore been concluded that the two processes mentioned above, viz., reflexion, and excitation of secondary rays beginning at 11 volts, are the only causes of electrons leaving the impacted surface. It was found by Baeyer that with a minimum velocity of impact of about 25 volts more electrons leave the plate than fall on it, and this result, combined with the fact that Campbell detected a positive current (presumably from a positively charged plate) when the bombarding electrons had a minimum velocity of 30 volts, has given rise to the view that the second process—that which is operative above 11 volts—is an ionisation at the metal surface, the material ionised being either the metal itself or gas attached to it. On this view it is concluded that the critical velocity of 11 volts is the “ionisation potential ” of the material ionised. This velocity was found to be the same for all the metal surfaces tested, and as it agreed with the usually accepted value of the “ionisation potential” for hydrogen, it has been suggested that the material ionised is hydrogen present in the surface of the metal. Some confirmation of this view has been obtained by Campbell from experiments with metal surfaces subjected to treatment designed to modify the amount of hydrogen present, but the evidence hitherto produced cannot be said to prove conclusively that the process which begins at 11 volts is a genuine ionisation by electron collisions. That ionisation occurs ultimately can hardly be doubted, for it has been observed that when the velocity of the electron stream is sufficiently increased, the number of electrons leaving a bombarded electrode is in some cases as much as twenty times as great as the number arriving at it, but the first direct proof that ionisation occurs at the metal surface when the impacting electrons have a velocity as small as 11 volts seems to be that given by the experiments made in the course of our investigation of the ionisation of helium. The present research is a fuller investigation of this effect, undertaken in order to ascertain whether the evidence of ionisation at 11 volts could be substantiated, and, if so, to determine whether it should be attributed to the metal itself or to hydrogen attached to the metal surface.

Emission of Electromagnetic Radiation by the Impact of Positive Ions of Hydrogen on Metal Surfaces

1956 ◽  
Vol 104 (5) ◽  
pp. 1492-1493 ◽  
Author(s):  
Rafi M. Chaudhri ◽  
Mustafa Yar Khan ◽  
Abdul Latif Taseer
Keyword(s):  
Electromagnetic Radiation ◽  
Metal Surfaces ◽  
Positive Ions ◽  
The Impact

scholarly journals The formation of negative ions by positive-ion impact on surfaces

1938 ◽  
Vol 168 (933) ◽  
pp. 284-301 ◽  
Keyword(s):  
Ionization Chamber ◽  
Metal Surfaces ◽  
Negative Ions ◽  
Negative Ion ◽  
Distribution Analysis ◽  
Positive Ions ◽  
Mass Spectrograph ◽  
Quantal Theory ◽  
Double Mass ◽  
Positive Ion

The quantal theory of negative ions has now been developed considerably (Massey and Smith 1936; Massey 1938), but on account of difficulties of computing it is usually necessary to assume rather than to prove that a given ion exists, and then to discuss the probability of its formation by different processes. The work described here is a contribution to the experimental side of this subject. It had its origin in a projected attempt to measure the capture cross-section of mercury atoms for electrons, as a verification of Massey and Smith's (1936) then unpublished theory of this process. In considering this it became clear that the experiment would be one of unusual difficulty. Before proceeding with it, therefore, it was decided to verify the existence of Hg - as a stable entity, which is assumed in the quantal theory. this was in doubt since Stille (1933), in some careful experiments, had recently failed to obtain it from the plasma of various forms of discharge through mercury vapour, although it is known that negative ions tend to accumulate in such regions (Emeleus and Sayers 1938). Whilst one of us was repeating his experiments, with modifications which led to essentially the same results and will be describes elsewhere, Arnot and Milligan (1936 b ) reported that they had obtained Hg - by bombardment of metal surfaces with Hg + . A comparison of their work with our own showed only one essential point of difference, namely that the construction of their apparatus did not permit of degassing in situ , a condition satisfied with our tubes. Both for this reason and because of the intrinsic importance of their discovery it was thought desirable to repeat part of their work, with apparatus geometrically similar in electrode construction, but capable of being degassed in a furnace under vacuum. We were again unable to obtain Hg - after the apparatus had been degassed and in operation for a short of that of Hg - was obtained. There were, however, always present several light negative ions, which had the excess energies found by Arnot and Milligan (1936 b ) with Hg - . The conditions under which these were formed led us to suppose that they were produced by bombardment of the metal surfaces by mercury positive ions (Press 1937; Sloane 1937) and not capture of electrons by positive ions of the same species, the process suggested by Arnot and Milligan (1936 b ). The existence of a process of this type, which may be conveniently termed "sputtering" (Sloane and Press 1938), is also implied by some earlier work by J. S. Thompson (1931) which has, so far as we know, never been published in detail. It is, however, impossible to decide definitely ion (e. g. CO - ) when it hits the surface, so long as one is producing the negative ions on a metal surface in a plasma or ionization chamber. One cannot overlook the possibility of the negative ion being formed from its own positive ion, since the latter may be present in the plasma or ionization chamber, and CO + , for example, was in fact shown in our work to be there from the positive-ion mass spectra, although in quantity only a fraction of 1% of Hg + . An unambiguous decision on this point can only be reached by first isolating a particular positive ion by a mass spectrograph, then bombarding a surface by this in a high vacuum , and finally making a mass spectrographic and energy distribution analysis of the resultant negative ions. We have built a double mass spectrograph for this purpose and find that negative ions of one kind possessing energies in excess of that imparted to them by the accelerating fields can be produced by bombardment with positive ions of another kind (Sloane and Press 1938). An account of the experiments with the single mass spectrograph is given in 1. the experiments with the double mass spectrograph are described in 2.

Adsorption and desorption of positive ions on glass and metal surfaces

Vacuum ◽  
1959 ◽  
Vol 9 (1) ◽  
pp. 79
Author(s):  
J.H. Leck
Keyword(s):  
Metal Surfaces ◽  
Adsorption And Desorption ◽  
Positive Ions

Hyperthermal surface ionization of some organic molecules on metal surfaces

2000 ◽  
Vol 459 (3) ◽  
pp. L493-L497
Author(s):  
V.N. Ageev ◽  
S.Y. Davydov
Keyword(s):  
Metal Surfaces ◽  
Organic Molecules ◽  
Surface Ionization

scholarly journals The liberation of electrons from metal surfaces by positive ions. Part II.—Theoretical

1930 ◽  
Vol 127 (805) ◽  
pp. 388-406 ◽  
Keyword(s):  
Electron Emission ◽  
Metal Surfaces ◽  
Secondary Electron ◽  
Thermal Contact ◽  
Secondary Electron Emission ◽  
Present Knowledge ◽  
Theoretical Treatment ◽  
Positive Ions ◽  
Secondary Phenomenon ◽  
Positive Ion

In this paper we propose to consider the process of electron capture by positive ions at a metal surface, and the emission of electrons which occurs as a secondary phenomenon. The discussion which we venture to give is admittedly crude, and it is to be hoped that an adequate theoretical treatment of the problem will not be long delayed. As a preliminary we shall discuss some aspects of present knowledge regarding electrical conditions near metal surfaces. Recent experiments of Compton and van Voorhis suggest that positive ions capture an electron from a metal before making thermal contact with the surface, so we require to know the nature of the electric field at some distance from the mechanical boundary. We shall proceed to some calculations on the probability of neutralisation, basing our work on the supposition that neutralisation is due to auto-electronic emission under the influence of the electrostatic field of the approaching positive ion. We shall then discuss the phenomenon from the viewpoint of the transition of an electron through a potential barrier between two states of equal energy, and attempt to apply the results obtained to an explanation of the mechanism of secondary electron emission.

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