Photoionisation of Ca${}^{+}$ ions in the valence-energy region 20$\sim$eV~--~56$\sim$eV : experiment and theory

Abstract

Relative cross sections for the valence shell photoionisation (PI) of ${}^2\mathrm{S}$ ground level and ${}^2\mathrm{D}$ metastable Ca${}^{+}$ ions were measured with high energy resolution by using the ion-photon merged-beams technique at the Advanced Light Source. Overview measurements were performed with a full width at half maximum bandpass of $\Delta E=17$~meV, covering the energy range 20~eV -- 56~eV. Details of the PI spectrum were investigated at energy resolutions reaching the level of $\Delta E=3.3$~meV. The photon energy scale was calibrated with an uncertainty of $\pm 5$~meV. By comparison with previous absolute measurements %by Kjeldsen et al in the energy range 28~eV -- 30.5~eV and by Lyon et al in the energy range 28~eV -- 43~eV the present experimental high-resolution data were normalised to an absolute cross-section scale and the fraction of metastable Ca${}^{+}$ ions that were present in the parent ion beam was determined to be 18$\pm$4\%. Large-scale R-matrix calculations using the Dirac Coulomb approximation and employing 594 levels in the close-coupling expansion were performed for the Ca${}^{+}(3s^{2}3p^{6}4s{}^2{\text{S}}_{1/2})$ and Ca${}^{+}(3s^{2}3p^{6}3d{}^2{\text{D}}_{3/2,5/2})$ levels. The experimental data are compared with the results of these calculations and previous theoretical and experimental studies.

19 pages, 14 figures, 3 tables

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Cited by in corpus (1)

• Single photoionization of the Kr-like Rb II ion in the photon energy range 22 - 46.0 eV