Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2021 / Paper 2A / Section A / 16 / b / Solution

For $B\gg {\Delta }_o$, the corresponding asymptotic expansion isHenceAt zero field, $E_0,E_1,E_3$ converge to the ${}^{3}F$ atomic term and $E_2$ to ${}^{3}P$ at $15B$. The ${}^3{T}_{1g}(P)$ branch therefore has zero initial slope; its high-field slope is not zero.