Abstract

The energies of the Ni-like ions with Z=36-51 are calculated. The energies of the low 3d 3/2 4d 3/2 [J=1] and upper 3d 3/2 4f 5/2 [J=1] working levels of the self-photopumped X-ray laser are analyzed along the sequence. We studied irregularities in the crossing Z-points of each working level with another level of the same parity. The irregularities are the features of the energy levels and of the radiative transition probabilities (RTP) associated with this level. They result in a decrease in the radiative transition probability (RTP) in one transition channel and an enhancement of RTP in another channel. The list of elements that lase on the self-photopumped transition can be extended much further than originally known. We present the first calculation of the wavelengths of this transition in Ni-like sequence to Z = 79 using the relativistic perturbation theory with a zero approximation model potential.