The Ca I absorption spectrum in the extreme ultraviolet: excitation of the 2p subshell

Abstract

The Ca I absorption spectrum has been photographed between 10 and 120 Å for the first time. At least seven discrete features – all attributable to excitation of the 2p subshell – have been observed. Identifications are made by comparison with Hartree–Fock calculations. The Hartree–Fock results also support an explanation of the irregular quantum defects and remarkable breadths of the lines assigned to the 2p→3d transition.