Search

Poly(1,4–phenylene-methylidynenitrilo-1,4–phenylenenitrilomethylidyne) (PPI) backbone approximated with poly(p-phenylene vinylene)like polymer composed of alternate phenylene and vinylenelike units is treated within π electron approximation in terms of the chain composed of united atoms built up of virtual benzene and ethylene atoms. Electronic structure of the united atom is derived from interactions of benzene p and β bands with V band of ethylene, taking into account that continuity of their π systems results from overlap of vinylenelike highest occupied molecular orbital and lowest unoccupied molecular orbital orbitals with relevant components of benzene molecular orbitals having phase at parapositions. Electronic band structure has been derived within π-electron approximation in a way resembling tight binding approximation usually applied to semiconductors. The proposed model is suitable to interpret UV-visible spectra of PPI with additional explaining vibronic progressions. Additionally, an expected location of lone pair related level is proposed. [ABSTRACT FROM AUTHOR]

Transmission and fundamental reflectivity studies, completed on amorphous Zn-P thin films, allowed us to obtain parameters describing the fundamental absorption edge, i.e., the optical pseudogap EG, Urbach energy EU and exponential edge parameter ET. All these data, together with the results of earlier transport measurements, have been utilized in developing simple models of electronic structure (distribution of electronic states) for amorphous Zn-P thin films of two compositions, i.e., Zn57P43 (near stoichiometry of Zn3P2) and Zn32P68 (near stoichiometry of ZnP2). [ABSTRACT FROM AUTHOR]