An investigation of the parameters of high-frequency discharge plasma at intermediate pressures by spectroscopic methods

The measured absolute and relative intensities of spectral lines are used to study the characteristics of a strongly nonequilibrium high-frequency discharge plasma at intermediate pressure in helium, in which the electron distribution function over energies contains groups of "slow" and "fast" electrons. It is established that the effective temperature of "slow" electrons $T_e{}^M$ is 0.15-0.25 eV, and the contribution by their ionization to the total electron concentration is of the order of $10^{12}-10^{13} cm^{-3}$. We determine the population of the highly-excited energy levels of He atoms for the principal quantum number $n=4-14$. The obtained low values of $T_e{}^M$ are explained by the presence of electron beams in the discharge.