The Ca I absorption spectrum in the vacuum ultraviolet: excitation of the 3p-subshell

The Ca I absorption spectrum between 300 and 800 Å (41-10 eV) has been photographed revealing at least 125 new lines. All the stronger lines are identified by comparison with Hartree-Fock calculations. In addition to single electron excitation of the 3p-subshell there is clear evidence of a simultaneous excitation of the 4s valence subshell and a 3p-subshell electron. The more important processes of multi-electron excitation are indicated. The general case of 3p → 3d excitation in elements Z ═ 18 to 28 is discussed and is illustrated by plots of the effective central potentials for 3d wavefunctions derived from the Hartree-Fock results.