title: Toward assessment of density functionals for vibronic coupling in two-photon absorption: A case study of 4-nitroaniline.
abstract: In this study, we predict vibronic two-photon absorption (TPA) spectra for 4-nitroaniline in vacuo. The simulations are performed using density functional theory and the approximate second-order coupled-cluster singles and doubles model CC2. Thereby we also demonstrate the possibility of simulations of vibronic TPA spectra with ab initio wavefunction methods that include electron correlation for medium-sized systems. A special focus is put on the geometric derivatives of the second-order transition moment and the dipole moment difference between the charge-transfer excited state and the ground state. The results of CC2 calculations bring new insight into the vibronic coupling mechanism in TPA spectra of 4-nitroniline and demonstrate that the mixed term is quite large and that it also exhibits a negative interference with the Franck-Condon contribution.
authors.affiliation: Department of Physical and Quantum Chemistry, Faculty of Chemistry, Wrocław University of Technology, Wyb. Wyspiańskiego 27, PL-50370, Wrocław, Poland; Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, SE-10691, Stockholm, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Zaleśny
authors.forename: Guangjun
authors.initials: G
authors.lastname: Tian
authors.forename: Christof
authors.initials: C
authors.lastname: Hättig
authors.forename: Wojciech
authors.initials: W
authors.lastname: Bartkowiak
authors.forename: Hans
authors.initials: H
authors.lastname: Ågren
keywords: CC2 method; density functional theory; excited states; range-separated hybrid functionals; two-photon absorption; vibronic coupling