Electron-impact ionization and ionic fragmentation of O2 from threshold to 120 eV energy range

We study the electron-impact induced ionization of O2 from threshold to 120 eV using the electron spectroscopy method. Our approach is simple in concept and embodies the ion source with a collision chamber and a mass spectrometer with a quadruple filter as a selector for the product ions. The combination of these two devices makes it possible to unequivocally collect all energetic fragment ions formed in ionization and dissociative processes and to detect them with known efficiency. The ion source allows varying and tuning the electron-impact ionization energy and the target-gas pressure. We demonstrate that for obtaining reliable results of cross-sections for inelastic processes and determining mechanisms for the formation of O[Formula: see text]([Formula: see text]) ions, it is crucial to control the electron-impact energy for production of ion and the pressure in the ion source. A comparison of our results with other experimental and theoretical data shows good agreement and proves the validity of our approach.

Cavitating Vortex Flow Generated by a Stationary Volute Casing and a Rotating Centrifugal Impeller

Three devices for treating contaminated water using a cavitating vortex have been developed and tested. The first device uses stationary twin volute casings to generate cavitating vortices. Observation of the collisions among the opposing counter-rotating vortices revealed that their end portions whirl, that the vortices never collide head-on, and that they eventually separate into several small vortex strings. The second device is simply half of the first device. A single volute casing is used, and the vortex flow collides with a solid wall. The third device uses a centrifugal impeller and a circular swirling chamber to generate a cavitating vortex. A high absolute circumferential velocity at the impeller exit induces a strong vortex in the chamber. The vortex cavitation is smoother than in the first two devices, and the end portion of the vortex whirls in the same manner as that generated in the first device. Installation of an orifice at the exit of the swirling chamber reduced the diameter of the flow passage and thereby accelerated the rotating and axial flow velocities. Testing showed that this third device produces fine, even-sized cavitation bubbles that are uniformly distributed in the collision chamber, which is the ideal condition for water treatment.

The Attachment of Low-Energy Electrons to Dicyanogen in the Gas Phase

The negative ions C-, CN- and C2N- formed by the dissociative resonance attachment of low-energy electrons to dicyanogen in the gas phase have been studied over the electron impact energy range from 0 to 15 eV. The formation of the CN- ion was studied by using a 'monochromatic' electron gun and the translational energy of the ion measured as a function of the electron energy across the dissociative resonance capture curve. An energy balance analysis for CN- ion formation has been used to propose the electron capture processes and to construct a potential energy diagram (for C-C internuclear separation) for CN- ion formation. The molecular ion, C2N2-, has been shown to result from the associative resonance attachment of thermalized electrons scattered from the collision chamber surfaces and to exhibit an autodetachment lifetime in the microsecond timerange.

Dissoziativer Ladungsaustausch von He+ -und Ne+ -Ionen mit den Molekülen N2, O2 und CO2 bei Stoßenergien von 3 bis 200 eV

Cross sections for the dissociative charge transfer reactions He+ + N2, O2 and Ne+ +N2 , O2, CO2 have been measured over an energy range from 3 to 200 eV and are compared with values given by other authors. The values were determined from measurements of the current of the slow charge exchange ions formed within a collision chamber.

Gaseous and surface reactions involving helium metastable atoms and resonance photons

The absolute electron yield ( γ M ) for He (2 3 S ) metastable atoms incident on a gold surface has been measured. The method requires passage of a metastable atom flux through a collision chamber containing argon and thence to the gold surface. From observations on the current of argon ions arising from collisions of the type He (2 3 S ) + A → He + A + + e , together with measurements of the electron emission from the gold surface, γ M may be determined. The total cross-sections for collisions between metastable helium atoms and He, Ne, A and K have been measured and in the asymmetrical cases are observed to rise linearly with increasing atomic number of the target atom. Some collisions involving helium resonance radiation have also been studied. In particular, the photo-electric yield from the gold surface has been determined together with the attenuation of the photon flux in passage through certain noble gases.