Account of the fine structure of hydrogen atom levels in the effective emission cross sections of Balmer lines excited by electron impact in gases and plasma

The possibility of a correct account of the fine structure was shown for two limiting cases observed in beam and plasma experiments. A significant difference was found in the emission cross sections and the rate coefficients of direct and dissociative excitation of the H α and H β lines by electron impact in two limiting cases (e.g., this difference reaches an order of magnitude for dissociative excitation of the H β line). The most reliable data on the cross sections and the rate coefficients of direct and dissociative excitation of the H α and H β lines by electron impact were found for both limiting cases. It was shown that, among the first four lines of Balmer series (rather easily detected), only the first two lines, i.e., H α and H β, can be currently employed in plasma spectroscopy studies because of the absence of data on the partial excitation cross sections of hydrogen atom nl-sublevels with n≥5.