Answer
The potential energy function is lower inside the corral than it is at the locations of the iron atoms.
Work Step by Step
A standing wave pattern is visible inside, reminiscent of the pattern in Figure 40.16. The electron is trapped within a finite potential well, which indicates that the potential energy function is lower inside the corral than it is at the locations of the iron atoms.
If the potential energy function were higher inside the corral than it is at the locations of the iron atoms, we would see an exponentially decreasing tail for the wavefunction, equation 40.40.
