Journal of Physical Studies 26(1), Article 1301 [18 pages] (2022)
DOI: https://doi.org/10.30970/jps.26.1301

RESONANCES IN THE ELECTRON SCATTERING FROM A CALCIUM ATOM

V. F. Gedeon, V. Yu. Lazur , S. V. Gedeon, O. V. Yegiazarian

Uzhhorod National University, 54, Voloshyn St., Uzhhorod, UA–88000, Ukraine

Received 04 November 2021; in final form 21 December 2021; accepted 21 December 2022; published online 07 February 2022

With the use of term-dependent non-orthogonal orbitals and B-splines as basic functions, an extended BSR-version of the $R$-matrix method was developed, which effectively takes into account the effects of electronic correlation and polarization of the target by the incident electron. Using this version, a systematic study of electron scattering on a neutral calcium atom in the range of collision energies up to 4.3 eV was performed. The strong coupling method with the term-dependent non-orthogonal orbitals sets and the spline representations of basis functions was used for the accurate representation of the wave functions of the target. The close-coupling expansion includes 39 bound states of neutral calcium, covering all states from the ground state to $4s8s \;^1S$. The study has revealed a strong sensitivity of the scattering cross sections to the effects of electronic correlation in both the $N$-electron target and the $(N+1)$-electronic collision system. It is shown that taking into account valence and core-valence electron correlations by mixing the configuration of the ground state of the target atom with additional configurations with single- and double- excited core significantly improves the agreement of the calculated integral and partial e+Ca-scattering cross sections with the experiment. The complex resonance structure of the angle-integrated total cross-section of the elastic е+Са-scattering and the excitement of $4s4p\;^3P^\mathrm{o}$, $3d4s\;^3D^\mathrm{e}$, $3d4s\;^1D^\mathrm{e}$, $4s4p\;^1P^\mathrm{o}$ and $4s5s\;^3S^\mathrm{e}$ states of Ca atom by the electron impact were studied in detail. The observed structures were associated with particular autodetachment states of the incident electron+Ca atom system. The position and the width of the detected resonances were determined and their spectroscopic classification was made.

Key words: electron, calcium atom, scattering, excitation, ionization, $R$-matrix with $B$-splines method, nonorthogonal orbitals, resonances.

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