Theoretical study of the vertical electron excitation of linear carbon clusters C-3, C-5, and C-7

Abstract

The vertical electron excitation spectra of linear carbon clusters C-3, C-5, and C-7 have been investigated by means of polarization propagator calculations using the second-order algebraic diagrammatic construction [ADC(2)] scheme. The structure of singlet and triplet excited-state manifolds below the lowest ionization threshold has been analyzed in detail for the smallest prototype cluster C-3. The electronic spectra of all three molecules contain numerous low-lying single and double valence excitations, reflecting strongly the correlated nature in these clusters. The density of the excited states becomes increasingly high above the onset of Rydberg excitations. A substantial mixing of various valence and Rydberg configurations in this region does not allow for simple interpretation of the final electronic states. The spectroscopic and photophysical implications of this complex situation are discussed. Where possible the computed excitation energies and oscillator strength are compared with available experimental and previous theoretical data. (C) 2001 John Wiley & Sons, Inc.