Solution (source code)

= Solution

Using $\sin^2u=\tfrac12-\tfrac14e^{2iu}-\tfrac14e^{-2iu}$, the <energy eigenstate> decomposition is
$$
\boxed{\Psi(0,x)=\mathcal N\sqrt{2\pi R}\left(\frac12\phi_0(x)-\frac14\phi_2(x)-\frac14\phi_{-2}(x)\right).}
$$
Only the <energy eigenvalues> zero and $E_\star=2\hbar^2/(mR^2)$ occur. The last two terms are distinct <momentum eigenstates> in the same <energy eigenspace>.