Photoionization cross-sections of valence ns and np (n = 2,3) atomic shells in soft x-ray region

Theoretical photoionization cross-sections for average of configuration terms of valence ns- and np- shells of atoms C, N, O, F, Ne, Si, P, S, Cl and Ar are calculated with account for intrachannel and interchannel interactions for the energy region from threshold to 400 eV. The many-electron effects were accounted for within the framework of RPAE (random phase approximation with exchange) method, which is extended for average terms of unfilled shells. Calculations demonstrate for open-shell atoms similar effects as that were known for noble gas atoms Ne and Ar, namely a strong decrease of photoionization cross-sections of ns- subshell due to the interaction of transitions $ns\to \epsilon p$ and $np\to \epsilon d$.