LUMO

Subadjacent orbitals: NHOMO and SLUMO

If existent, the molecular orbitals at one energy level below the HOMO and one energy level above the LUMO are also found to play a role in frontier molecular orbital theory. They are named NHOMO for next-to-highest occupied molecular orbital and SLUMO for second lowest unoccupied molecular orbital. These are also commonly referred to as HOMO−1 and LUMO+1 respectively.