Position-space and momentum-space orbitals in polyenes

Here are the PI orbitals in order of increasing energy for a polyene with 20 carbon atoms. Orbitals are shown as + (red) and - (green) contours in the plane 1 unit of atomic distance above the molecular plane, together with the projected positions of the nuclei. Notice the resemblance to particle-in-a-box solutions.

Here are depictions of the same PI orbitals in momentum space