The highly excited-state manifold of guanine: calibration for nonlinear electronic spectroscopy simulations

摘要: A computational protocol based on the complete and restricted active space self-consistent field (CASSCF/RASSCF) methods their second-order perturbation theory extensions (CASPT2/RASPT2) is employed to benchmark highly excited-state manifold of DNA/RNA canonical purine nucleobase guanine in vacuo. Several RASPT2 schemes are tested, displaying a steady convergence electronic transition energies dipole moments upon enlargement toward reference values. The outcome allows calibrating optimizing efforts by considering cheaper more approximate RAS that could enable characterization manifolds multi-chromophoric systems, such as dimers or multimers. Simulations two-dimensional spectra show similar trends those observed other adenine, deviating from this pyrimidine nucleobases featuring its main absorption signal, embodied sizable double HOMO LUMO excitation contributions, UV probing window.