Accession Number : ADA264552


Title :   Triplet States and Optical Absorptions in Finite Polyenes and Conjugated Polymers


Descriptive Note : Professional paper


Corporate Author : NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA


Personal Author(s) : Campbell, David K ; Gammel, J T ; Lin, Hai-Qing ; Loh, Jr, E Y


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a264552.pdf


Report Date : Mar 1993


Pagination or Media Count : 22


Abstract : We study the nature of triplet states in correlated, quasi one dimensional bands, with emphasis on the half-filled case relevant to conducting polymers. To incorporate both electron-phonon and electron-electron interaction effects, we use a Peierls-extended Hubbard Hamiltonian, which we solve for finite systems via (numerically) exact diagonalization (Lanczos) techniques. We extend our results to polymers using both standard finite-size extrapolation techniques and a novel boundary condition averaging scheme. First, we examine the nature of the lowest triplet state, focusing on the crossover from the free electron picture of neutral soliton pairs to the strongly correlated limit of spin excitations. We then examine the optical absorption spectra spectra corresponding to (allowed) triplet-triplet transitions; for this purpose it is important that our naval boundary condition averaging method maintains sharp gap-edge features with reducing spurious rapid frequency variations produced by the finite-size approximations to the band-to-band continuum. We compare our results to data on triplet transitions in finite polyenes and discuss possible additional experimental implications, including the interpretation of recent spin-dependent photomodulation (SDPM) experiments in both trans-(CH)x and non- degenerate ground state conjugated polymers.... Triplet-triplet transitions, Band-to-band-continuum, Spin-dependent photomodulation(SDM)


Descriptors :   *OPTICS , *POLYMERS , *ELECTRONIC STATES , *ABSORPTION SPECTRA , FREQUENCY , CONDUCTIVITY , EXCITATION , FREE ELECTRONS , BOUNDARIES , FOCUSING , EXTRAPOLATION , SPIN STATES , SOLITONS , PHONONS , GROUND STATE , TRANSITIONS , STANDARDS , ELECTRONS , VARIATIONS , ONE DIMENSIONAL , EDGES , INTERACTIONS , NEUTRAL


Subject Categories : Polymer Chemistry
      Electricity and Magnetism
      Atomic and Molecular Physics and Spectroscopy
      Solid State Physics


Distribution Statement : APPROVED FOR PUBLIC RELEASE