The highest occupied molecular orbital is called the HOMO and the lowest unoccupied molecular orbital is called the LUMO; the energy gap between these two states is known as the HOMO-LUMO gap.
Den højestokkuperede molekylorbital kaldes HOMO og den lavest ikke-okkupedere molekylorbital kaldes LUMO; energikløften mellem disse to stadier kendes som HOMO/LUMO-kløften.