Modelling photoelectron spectra in solution: adenosine as a test case

We here describe a procedure for the calculation of PE spectra in solution, including vibrational and dynamical solvent effects. Steady-state vibronic spectra are computed in the harmonic approximation, including the effect of the electronic continuum on the cross section. Solvent effects are described in the framework of continuum polarizable models, providing an accurate assessment of dynamical solvation effects, crucial for a reliable modelling of PE processes, with a very small computational cost. Time-resolved PE spectra are computed from the nonadiabatic quantum dynamics of the electronic-vibrational wavepacket propagating on the coupled valence states, described with a linear vibronic coupling model and adopting a semiclassical approximation. Our approach provides accurate steady-state PE spectra for 9(H)adenine in the gas phase and adenosine in water. In the former case, the position, the relative energy and the dependence on the PE ejection angle for the three lowest-energy bands are in good agreement with the experimental ones. We simulated the pump-probe PE spectrum of adenosine in water using both static and dynamical approaches, obtaining spectra fully consistent with the experimental ones and getting new insights on its sub-ps photophysics. Some methodological issues in the simulation of PE spectra in solutions are also discussed.