Electron-Impact Excitation of the 5p55d6s2 Autoionizing States in Ba Atom

Abstract

The excitation cross-sections for the 5p55d6s2 autoionizing states of Ba atoms are studied experimentally and theoretically in an electron-impact energy range from the excitation thresholds of the states up to 600 eV. Experimental data are obtained by determining the intensities of lines in the ejected-electron spectra measured at an observation angle of 54.7∘. The incident-electron and ejected-electron energy resolutions are 0.2 eV and 0.07 eV, respectively. The calculations are performed in the distorted wave approximation by using relativistic radial wave functions obtained in the standard Dirac–Fock–Slater method. For all the states, the experimental cross-sections reach their maxima at low impact energies revealing by that predominantly the spin-exchange character of the excitation of autoionizing states. The structure of the near-threshold maxima indicates the formation of strong negative-ion resonances. At high impact energies, the shape and value of the cross-sections are determined by configuration and state mixing effects.

Excitation Dynamics of the 5p^6 Auger Spectra in Ba + e^– Collisions

“…The spectroscopic assignment and the analysis of the decay channels of the 5p 5 𝑛𝑙𝑛 ′ 𝑙 ′ 𝑛 ′′ 𝑙 ′′ states in Ba atoms [14] have shown that reaction (4) is the most preferred channel for the decay of atomic states with excitation thresholds above 21 eV. Their resonant excitation character [15] explains the rapid increase in the ionization cross-sections at threshold energies.…”

“…The Auger spectra corresponding to the decay of the 5p 5 𝑛𝑙𝑛 ′ 𝑙 ′ states (see reaction (3)) were measured by employing the electron spectrometer [11] shown schematically in Fig. 1.…”

Excitation-autoionization contribution to single ionization of Sr by electron impact

“…The measurements were carried out on a electron-atom collision setup, which has been previously employed in a number of studies of the electron spectra of metal vapors [34,35]. In the present study, two different sources of incident electrons have been employed: an electrostatic 127°monochromator with the energy resolution of 0.2eV (FWHM) was used for the near-threshold energy region and a five-electrode electron gun with the energy spread of the beam 0.5eV (FWHM) was used at the energies beyond 50eV [36].…”

Electron-impact ionization of the 4p6 subshell in strontium

“…The energy spectrum of Auger electrons e A lies between 10.2 and 18.4 eV and, therefore, it partially overlaps with the spectrum of ejected electrons formed due to the decay of the 4p 5 nln ′ l ′ n ′′ l ′′ atomic autoionizing states [19][20][21][22][23]. However, the study of ejected-electron spectra in a wide range of impact energies, including in the near-threshold region, makes it possible to distinguish atomic and Auger lines due to the higher excitation thresholds of the latter.…”