Yu. A. Piotrovskii

On the mechanism of formation of helium molecules in a low-temperature plasma

The glow of He2 molecules in a low-pressure (P ≤ 2 Torr) helium plasma excited by a monochromatic electron beam is detected and studied. The experimental data point to the existence of two basic mechanisms of formation of an excited He2 molecule, namely, the collision of an excited helium atom with two unexcited atoms and the recombination of a molecular ion.

Specific features of the excitation spectrum of helium II in a plasma initiated by an electron beam

The emission of a low-pressure helium plasma (P≤2 Torr) initiated by a monochromatic electron beam is investigated. It is found that an increase in the current leads to a drastic increase in the rate of charge exchange of doubly charged helium ions. The assumption is made that inelastic collisions of He++ ions with metastable helium atoms provide the main channel of charge exchange of these ions due to the reaction He+++Hem→ He+*+He0+.

A new channel of the concentration decay of doubly charged helium ions in a plasma

A model describing the decay of concentrations of excited helium atoms and ions taking into account doubly ionized helium is constructed on the basis of experimental data on excitation of a helium plasma by a pulsed electron beam. From this model, the rate constant of reaction He+++Hem→He++He0+ is estimated. It is found to agree in order of magnitude with theoretical estimates made in the framework of a model of polarization capture.