Ch 2.5 An energy eigenstate: $\hat{H}|\psi_n\rangle = E_n|\psi_n\rangle$. In a stationary state, the probability density $|\psi|^2$ and all expectation values are time-independent, even though the wave function has a time-dependent phase $e^{-iE_nt/\hbar}$. *See also:* Energy eigenstate, Time evolut