We report results on ab initio calculations of excited states of the
fullerene molecule by using configuration interaction (CI) approach with singly
excited determinants (SCI). We have used both the experimental geometry and the
one optimized by the density functional method and worked with basis sets at
the cc-pVTZ and aug-cc-pVTZ level. Contrary to the early SCI semiempirical
calculations, we find that two lowest 1T1uββ1Agβ electron
optical lines are situated at relatively high energies of ~5.8 eV (214 nm) and
~6.3 eV (197 nm). These two lines originate from two 1T1uββ1Agβ transitions: from HOMO to (LUMO+1) (6huββ3t1gβ) and from (HOMO--1)
to LUMO (10hgββ7t1uβ). The lowest molecular excitation, which is the 13T2gβ level, is found at ~2.5 eV. Inclusion of doubly excited determinants
(SDCI) leads only to minor corrections to this picture. We discuss possible
assignment of absorption bands at energies smaller than 5.8 eV (or Ξ»
larger than 214 nm).Comment: 6 pages, 1 figure, 9 Table