Coulomb inter-electron repulsion always becomes more severe for lower electron energy.

This is explained by the similarity of the electron energies at the 5f, 7s and 6d shells.

How near depends on the electron energy.

The electron energy is set by the electrical potential difference (voltage) between the sample and the tip.

In those cases other factors can scramble the electron energies.

These are very specific frequencies corresponding to the differences between electron energies in the atoms.

The Schrodinger model, with its fuller description of electron energies and probable locations, is able to do more than that.

This effect is due to Landau quantization of electron energy in an applied magnetic field.

Such a transport regime has been found to depend on the nanoribbon edge structure and the electron energy.

This constraint automatically permitted only certain values of electron energies.