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"Electron excitation of the np6 subvalence shell in rubidium (n = 4) and barium (n = 5) atoms"



Roman  V. I., Hrytsko V.V.


Using the electron spectroscopy method and the crossed electron-atom beam technique, the excitation dynamics of scattered and ejected electron spectra in rubidium and barium atoms was investigated in the impact energy region from the excitation thresholds of the p6 shell up to 600 eV. The spectroscopic classification of lines was performed by using the results of theoretical calculations of excitation energies, cross-sections, and decay rates for the nр5n1l1n2l2 states in rubidium, and 5р5n1l1n2l2n3l3 states in barium atoms. The optically forbidden autoionizing state in Rb2 molecule was revealed. The absolute effective excitation cross-sections for atomic and molecular autoionizing states were obtained. The strong resonance excitation was revealed in the near-threshold impact energy region caused by the formation of short-living states (resonances) of negative ions. The excitation energies, spectroscopic classification and decay channels for such states were determined. The effect of the post-collision interaction in ejected-electron spectra of rubidium atoms was investigated. The absolute value of the autoionization cross-section and its impact-energy dependence were obtained for rubidium atoms. The maximal relative contribution of autoionization to the total single ionization cross-section by electron impact was estimated to be 32% for rubidium atoms.

The applicationimportance of the resultsconsists in theextensive use of alkali and alkali-earth metalsas the main or additional component of different plasma environments, including the optical frequency standards and lasers in the ultraviolet optical range. The obtained data on absolute electron-impact excitation cross-sections and decay channels of autoionizing and negative ion states will be used for diagnostics of the energy and charge composition of various types of laboratory plasma, as well as for analyzing the spectral distribution of radiation of plasma in different gas-discharge devices.

The results of investigations are published in 8articles (including 3 in international journals) and as 20abstracts of Ukrainian and international scientific conferences. The author works are cited in 5 scientific journals, the overall index of citation is 35 (of these 9 are accordingly to the Scopus database).