complications without expansion homepage › Forums › a nucleus with a general shape ? › complications without expansion This topic has 0 replies, 1 voice, and was last updated 3 years ago by Manon. Viewing 1 post (of 1 total) Author Posts March 2, 2020 at 3:22 pm #2739 Score: 0 ManonParticipant The 1/|r_e – r_n| factor in the formula on slide 9 makes it practically impossible to solve. Also, if we try to solve it exactly, there would be no need for perturbation theory. We need the expansion to be able to apply perturbation theory. Author Posts Viewing 1 post (of 1 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Log In