HOMO in addition to LUMO

In chemistry, HOMO & LUMO are rank of molecular orbitals. a acronyms stand for highest occupied molecular orbital together with lowest unoccupied molecular orbital, respectively.

Subadjacent orbitals: NHOMO and SLUMO

If existent, the molecular orbitals at one power level below the HOMO and one power to direct or imposing 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 included to as HOMO-1 and LUMO+1, respectively.