Positive Oxygen Ions Research Articles

The interaction of atomic particles with solid surfaces at intermediate energies II. Scattering processes

Measurements were made of the energy distributions of charged particles emitted from targets of platinum, nickel and molybdenum bombarded by atomic and molecular positive ions of hydrogen, deuterium , helium , carbon, nitrogen, oxygen, neon, argon and carbondioxide, with energy 2 to 40 keV. It is shown that the scattering of incident particles is predominantly elastic and approximately independent of the charge state of the incident particle. Hydrogen, deuterium, carbon and oxygen are scattered with both positive and negative charges, but CO2gives only negatively charged scattered particles. Scattering with positive charge increases over an energy range 2 to 15 keV per incident particle, while scattering with negative charge increases to a maximum at incident energies 3 to 7 keV per particle and then decreases up to the highest energies used, 40 keV. Scattering with positive and negative charges is of the same magnitude at the incident energy corresponding with the maximum for negative scattering of hydrogen ions. The energy distribution of negatively charged scattered ions is generally broader than that for positively charged scattered ions at the same incident energy, for the lighter ions. Scattering as neutral atoms is estimated roughly and is shown to increase rapidly as the bombarding energy is reduced below about 10 keV.

Drift velocity measurements for positive oxygen ions in oxygen

Results obtained for the drift velocities of positive oxygen ions in oxygen for E/N less, similar 450 × 10-17 v cm2 are described. The data confirm recent observations by Dutton and Howells.

Charge transfer reactions of nitric oxide with atomic and molecular ions of oxygen and nitrogen

The cross sections for charge transfer in collisions between nitric oxide and atomic and molecular positive ions of oxygen and nitrogen have been measured in the energy range from 3 to 200 ev in a crossed-beam experiment. A smooth interpolation is made between these results and the rate coefficients obtained at thermal energy by the afterglow technique. The dependence of these cross sections upon the energy of the electrons used to produce the primary ions has also been investigated to gain insight into the importance of the states of excitation of the primary ions.

Use of etched metal foils for production of positive ions for field ionization mass spectrometry

A platinum foil 8 μm thick was etched electrolytically in 3% potassium cyanide solution to form an edge which was much more efficient than a razor blade edge for producting positive ions of oxygen and nitrogen by field ionization. The etched foils were used in a mass spectrometer ion source to ionize these gases. Etched gold foil was also used to ionize the gases and was more effective than a razor blade. Attempts to improve the efficiency of razor blades for field ionization by etching and other procedures were not successful.

Emission of negative ions of oxygen from dispenser cathodes Part 1. - Cathodes of barium oxide in sintered nickel

Cathodes of sintered nickel and barium oxide have been used as ion sources in simple mass spectrometers and have been found to emit negative ions of atomic oxygen for at least 24 hours during their activation at 1250-1350° K. The evidence suggests that the oxygen is produced by the dissociation of barium oxide and is removed from the cathode by positive ion bombardment. At voltages greater than the ionization potentials of the residual gases, the variation of the oxygen ion current I with time t could be expressed as the sum of two exponentially decreasing terms: I = a exp ( - pt) + b exp ( - qt), where p and q were of the order of 2 and 0.2 per hour respectively. Similar results have been obtained with a commercial cathode containing triple carbonates. There appear to be two processes operating in parallel, corresponding to the two terms of the equation. It is postulated that the first process is the diffusion of oxygen through the bulk of the crystals to the nickel part of the cathode's surface, and its removal from there by bombardment with positive ions of oxygen and nitrogen. The second process is the diffusion of oxygen through the pores of the cathode, and its removal from the ends of the pores by bombardment with positive ions of barium as well as of the residual gases. The first process has the slower rate of replacement of oxygen and in an hour or two this process is insignificant compared with the second one. If the cathode's surface is temporarily poisoned with oxygen from an external source then it rids itself of the extra oxygen within a few seconds.

The adsorption of oxygen and hydrogen on platinum and the removal of these gases by positive-ion bombardment

An account is given of the results of measurements of the contact potential-difference between a tungsten filament and a platinum anode after the latter has been subjected to various treatments. It is shown that a clean platinum surface can be obtained by successive bombardments of the anode with positive ions of oxygen and of argon. The work function of a surface so prepared is found to be in good agreement with the most recent values obtained by thermionic measurements on clean platinum. Values are obtained also for the work functions of oxygen on platinum, hydrogen on platinum, and mixed layers of oxygen and hydrogen on platinum. The bearing of these results on the structure of the mixed layers is discussed.