Impact Of Metastable Atoms Research Articles

Penning ionization electron spectroscopy of organic molecules: stereochemistry of molecular orbitals

Abstract

Penning electron spectrum of ferrocene. evidence for steric effect on the electronic interaction causing penning ionization

The kinetic energy distribution of the elections ejected from ferrocene molecules by impact of thermal Ne( 3P 2) atoms was measured The iron 3d bands have very weak intensities relative to those of the ring π bands, suggesting that the iron orbitals are “shielded” by the cyclopentadienyl rings against the impact of metastable atoms

An Investigation of Physical Processes in a Hollow Cathode Discharge

The cathodes studied were similar to those used in the SERTII program and in the initial phase of the present work, except that bifilar heaters were employed. Triple carbonate was usually applied to the internal surfaces, although for long periods of operation, various barium dispensers were used. Experiments were conducted in a diode discharge system and mercury vapor was supplied from a conventional vaporizer. There is considerable evidence to suggest that electron emission occurs internally at constant current density J; about 2 to 5 x 10 amp/m. Although these values of J probably cannot be explained by simple thermionic emission despite the use of barium, considerable field-enhancement may occur in the presence of the dense internal plasma. This extends over an having a length determined by the current drawn. Electric fields E in the plasma sheath of about 10 v/m are necessary to account for observed data solely on the basis of this process. Another mechanism capable of giving the required current density and also relying on the presence of an internal plasma covering an active zone is the release of electrons by the impact of metastable atoms. High yields are expected when the excitation energy is close to the work function of the surface, as is the case for mercury impacting on tantalum, and the mechanism does not depend on the presence of an alkali metal. A small cylindrical Langmuir probe near the keeper orifice was used to measure electron temperature Te, electron number density ne and plasma potential Vp in the external plasma. It was also often convenient to use the keeper itself to obtain Te and Vp. Te was in the range 1 to 2.5 x 10K and increased with decrease of flow rate m and increase in /. The former dependence was ascribed to the fall of pressure with m, which resulted in the electrons gaining more energy between collisions. Te was independent of tip temperature T within the range 1000-1400°C. Vp was usually 14-19 v, decreasing as T was raised, and ne was about 10m~. To investigate the internal plasma a cylindrical Langmuir probe was inserted into a cathode. Te, derived from semilogarithmic plots, again decreased with increasing m (Fig. 1). The electron saturation current was used to estimate ne, which

Die auslösung von elektronen aus metallen durch metastabile atome, angewandt auf die messung von anregungsfunktionen

A method is described in which the liberation of electrons from solids by. impact of metastable atoms is used in the determination of excitation functions, relating to the production of metastable states in noble gases by collision with electrons. A beam of slow electrons passes through a cylinder K (fig. 1). At one side, opposite to an opening in this cylinder, a platinum plate P has been mounted. A part of the metastable atoms (and of the photons) produced by the electron beam hits the plate P and liberates electrons from it. The electron current thus arising is measured. Charged particles are kept away from the plate P by means of suitable magnetic and electric fields (§ 4). The effect of metastable atoms and that of photons are separated with the aid of a method in which alternating tensions are applied, making use of the relative slowness of the metastable atoms (§ 5).

Secondary Emission from Nickel by Impact of Metastable Atoms and Positive Ions of Helium

Experiments on the secondary electron emission from Ni electrodes due to bombardment by positive ions and metastable atoms in a helium discharge under conditions similar to those obtaining in a glow discharge are reported. The method of measurement is similar to that of Uyterhoeven and ${\mathrm{Harrington}.}^{1}$ The proportion of the measured current at the cathode which is carried by electrons is found to be 15 to 50 percent depending on experimental conditions. Similarly the number of electrons per slow positive ion is found to range between about 8 and 20 percent. The secondary electrons originate at the surface of the collector with about 15 volts maximum initial energy.

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

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.

Secondary Emission from Metals by Impact of Metastable Atoms and Positive Ions

Secondary Emission from Metals by Impact of Metastable Atoms and Positive Ions

Secondary Emission from Metals by Impact of Metastable Atoms and Positive Ions

Secondary Emission from Metals by Impact of Metastable Atoms and Positive Ions