engleski

Use of surface plasmons for manipulation of organic molecule quasiparticles and optical properties

Our recently proposed theoretical formulation based on Bethe–Salpeter G0 W0 methodology is applied here to explore the quasiparticle and optical spectra of anthracene (C14 H10 ) placed close to a metallic surface. Special attention is paid to explore how the energy shift and decay width of the low-lying anthracene bright excitons p, α and β depend on the type of the adjacent surface (described by the Wigner Seits radius rs ) and the separation from the surface. It is shown that p and α excitons weakly interact with surface excitations, but for rs ≈ 3 the intensive β exciton hybridizes with surface plasmon considerably, resulting in its splitting into two optically active modes. The β exciton decays extraordinarily fast ( ≈ 200 meV) to the electron–hole excitations in the metallic surface even for non-contact separations (z0 ≈ 12 a.u.). For rs > 5 the β exciton becomes infinitely sharp ( ≈ 0) and no longer interacts with the surface plasmon. Moreover, it is shown that HOMO and LUMO states near a metallic surface behave as statically screened rigid orbitals, with the result that the simple image theory arguments are sufficient to explain the HOMO–LUMO gap shift. Finally, it is demonstrated that the HOMO–LUMO gap shift dominantly depends on the position of the effective image plane zim of the adjacent surface.

organic molecule; optical spectra; GW-BSE

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