Lowest unoccupied molecular orbital delocalized state

It is important to note that many metallic properties, such as the Knight shift and the Korringa relationship, are determined by the finite and quasiFermi level local density of states ( p-LDOS). In the approximation most familiar to chemists, what this means is that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap in metals is much smaller than the thermal energy kf,T, and the value of the / f-LDOS reflects the frontier orbital contributions in a metallic system [23]. The /ip-LDOS also represents a crucial metal sxudace attribute that can serve as an important conceptual bridge between the delocalized band structure (physics) picture and the localized chemical bonding (chemical) picture of metal-adsorbate interactions. 

The conjugation, that is, the resonance interaction between the n bonds, results in delocalized n electron states. In the case of PPV these states are occupied by the eight n electrons. There is a highest occupied molecular n orbital, and there is a gap by extending up to next level, the lowest unoccupied molecular n orbital. 

---