Photoionization of doubly-charged Ca ions

We present measurements on the absolute photoionization cross section of do ubly-charged Ca ions in the photon energy range 50-70 eV, which encompasses resonances of the type 3s --> np. The energy dependence of the continuum c ross section differs from the earlier measurement by van Kampen et al (1997 ), but is reproduced quite well by a recent R-matrix calculation (Wilson et al 1999), although the estimates of the oscillator strengths of-the resona nce lines are too low.