U.S. Department of Energy


Date of this Version



Physical Review A 81, 053416 (2010); DOI: 10.1103/PhysRevA.81.053416


Absolute photoionization measurements were performed for a mixture of 2Po3/2 ground-state and 2Po1/2 metastable-state Ca3+ ions over the photon energy range 65.7–104.6 eV by merging an ion beam with a beam of monochromatized synchrotron radiation. The ionization threshold energy of the 2Po3/2 ground state was measured to be 67.063 ± 0.015 eV, which is 0.207 eV lower than the value tabulated in the NIST database. Most of the observed resonances associated with multiple Rydberg series of autoionizing states have been assigned spectroscopically using the quantum defect form of the Rydberg formula, guided by relativistic Hartree-Fock calculations of resonance energies and oscillator strengths. Intermediate coupling R-matrix calculations performed using the semi-relativistic Breit-Pauli approximation are in suitable agreement with measured absolute photoionization cross section in the energy range studied for this complex Cl-like ion species.