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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

LUMO (lowest unoccupied molecular orbital)

The lowest-energy molecular orbital that is empty. In a polyene with NN π electrons it is n=N/2+1n = N/2 + 1, the level just above the HOMO, and it receives the electron when the molecule absorbs light.

Particle-in-a-box wavefunction ψWavefunction between walls at x = 0 and x = L with 3 lobes and 2 interior nodes (marked with circles).V = ∞V = ∞0Lxψ

ψ3\psi_3, the LUMO of 1,3-butadiene: two nodes.

Example

β-Carotene has 22 conjugated π electrons: levels 1 to 11 are full, so the HOMO is n=11n = 11 and the LUMO is n=12n = 12. For 1,3-butadiene the LUMO is n=3n = 3.

See alsoHOMO (highest occupied molecular orbital)HOMO–LUMO gapExcited state