Thresholds of theK+Ldouble photoexcitation in argon

The argon photoabsorption cross section has been measured absolutely in the energy range around 3500 eV. Resonant K+L double photoexcitations and shake-up threshold jumps with an inner-shell 1${\mathit{s}}^1$2${\mathit{p}}^5$ double-hole configuration have been found. The observed energy positions agree quite well with those determined by relativistic self-consistent field calculations. Former determinations of the K+L shake-up threshold jump height have been confirmed.