Self-photopumped x-ray lasers from elements in the Ne-like and Ni-like ionization state

We report on experiments on the self-photopumped 3d ¹P₁→3p ¹P₁ and 4f ¹P₁→4d ¹P1 laser transitions in Ne-like and Ni-like ions, respectively. Lasing on the self-photopumped laser line has been observed for the first time for a number of elements including Ne-like V, Cr, Fe, and Co as well as Ni-like Ru and Pd. We have investigated the lasing process by varying the prepulse delay, which shows a shift of the optimum main pulse to second prepulse delays towards lower values with higher atomic number Z. Time-resolved measurements showed that self-photopumped and monopole collision-pumped lasing emission occurs essentially simultaneously. Accurate wavelength measurements and calculations are shown to be in excellent agreement.