[Pw_forum] add or remove electron energy

[kazempoor at ph.iut.ac.ir]

Dear All
I add one electron to an isolated atom and the difference in E(n+1)-E(n)=-0.09 Ryd but when I remove an electron from this atom 
I got E(n)-E(n-1)=-0.349 Ryd.
what is the reason for this difference? I think that this behavior is same for every system.
Thanks a lot 
Ali Kazempour
Physics Department, Isfahan University of Technology