Photoabsorption in the beginning of the neon isoelectronic sequence

The outer-subshell photoionisation is studied for the first five members of the 1s 2 2s 2 2p 6 isoelectronic sequence (Ne, Na + , Mg 2+ , Al 3+ ,l Si 4+ ). The ab initio calculations are performed in the random phase with exchange approximation (RPAE) in a way which treats consistently transitions to the 1s 2 2s 2 2pvs 1 P and 1s 2 2s 2 2p 5 vd 1 P excited discrete and continuous states. The evolution of photoabsorption phenomena as the ionisation degree increases is presented.