On the Franck-Condon effects in the absorption spectrum of C10H8 anion.: The analysis based on the ab initio MCSCF method

The near-IR, visible and UV regions of the absorption spectrum of naphthalene anion (C10H6-) are studied in terms of full optimized reaction space multiconfiguration self-consistent field method applied with Dunning's double-zeta basis set including polarization and diffuse functions on the all hydrogen atoms. Computed Franck-Condon activity of the all (nine) totally symmetric vibrations in the seven low-energy transitions is discussed and compared to the available experimental data. The assignment for some electronic transitions in the visible part of the naphthalene anion absorption spectrum is corrected on the base of full optimized reaction space multiconfiguration self-consistent field computations. We have argued that two (overlapping) bands at 21700 cm(-1) and 26800 cm(-1) are due to 1(2)B(1g) --> 1(2)A(u) and 1(2)B(1g) --> 2(2)A(u) transitions rather than to the short-axis and long-axis polarized ones as was suggested in an earlier semiempirical treatment. An experimental method appropriate to verify this result is proposed.