Solution
= Solution
The unperturbed ground state is even about $a/2$, while $V_{\mathcal E}=q\mathcal E(x-a/2)$ is odd. Its first-order expectation therefore vanishes.
= Solution
The unperturbed ground state is even about $a/2$, while $V_{\mathcal E}=q\mathcal E(x-a/2)$ is odd. Its first-order expectation therefore vanishes.