Abstract

For Ca, the localization of the 3d-orbital critically depends on the effective potential. In order to probe this in detail we have studied the 3p-absorption spectra of Ca, Ca^*, and Ca⁺ in the wavelength range 25 nm to 45 nm. The Ca was contained in a heat pipe operated at temperatures ⩾700°C. The VUV radiation of a (ruby) laser-produced plasma transmitted through the heat pipe was dispersed by a 1.5 m grazing incidence spectrometer. A multichannel photoelectric detector covering a spectral range of approximately 4 nm detected the dispersed VUV. Excitation and ionization was achieved by pumping the Ca 4s²¹S₀ → Ca 4s4p³P transition with a dye laser. Collisions convert the initial excitation into ionization. Various population densities have been probed by delaying the VUV continuum pulse relative to the initiation of the dye laser pulse. All spectra are dominated by a strong 3p → 3d resonance. Towards higher photon energies, the Ca and Ca⁺ spectra display sharp Rydberg lines whereas there are only broad structures in the Ca^* spectrum.

© 1986 Optical Society of America