Communication: Existence of the doubly excited state that mediates the photoionization of azulene

We use the high-level electronic structure computations based on the equation-of-motion coupled-cluster (EOMCC) theory to show that the previously postulated [V. Blanchet et al., J. Chem. Phys. 128, 164318 (2008)] doubly excited state of azulene, located below the ionization threshold and mediating the 1 + 2' multi-photon ionization that leads to a Rydberg fingerprint, exists. This supports the crucial role of doubly excited states in the Rydberg fingerprint spectroscopy, while demonstrating the usefulness of EOMCC methods in capturing such states. (C) 2013 AIP Publishing LLC.