Photoabsorption Spectra of Double- and Triple-Excitations above the Calcium 3p Threshold

Calcium triple photoexcitations leading to 3 p satellites have been observed by photoion spectroscopy measurements in the photoion energy region 35 to 42 eV. Monochromatized synchrotron radiation has been used for light source. The photoions are counted by discriminating the resultant calcium ionic charge states. Many photoion spectral peaks are found above the calcium 3 p double excitation region. Two series of triple excitation have been found; one starts at 37.1 eV and the other starts at 40.6 eV in photon energies. To gain a deep insight of the triple-electron excitations, multi-configuration Dirac-Fock calculations have been carried out. The photo-excited 3 p -vacancy states are found to be a strong mixture of 3 d , 4 s , and 4 p orbitals. A compact 3 d -orbital describes well the lower energy satellite resonances, whereas a diffuse 3 d -orbital describes well the higher energy satellite resonances.