The results of ab initio calculations that examine vertical and nonvertical transitions to several low-lying states of all-trans-octatetraene are presented. It is found that the lowest vertical excitation is to a valence π → π* ¹B_u state, and the nominally doubly excited 2¹A_g state occurs approximately 0.4 eV higher at the geometry of the ground state. Using estimated excited-state equilibrium geometries, we find that the 2¹A_g state is indeed the lowest singlet excited state, having a 0-0 tarnsition energy of 4.15 eV. The 0-0 transition energy for the 1¹B_u state is calculated to be 4.56 eV. The present results are compared with past theoretical and experimental results.
© 1988 American Chemical Society
Cave, R.J.; Davidson, E.R. “An Ab Initio Investigation of Several Low-Lying States of all- trans Octatetraene," J. Phys. Chem. 1988, 92, 2173. doi: 10.1021/j100319a019