The influence of the molecular charge on potential energy curves for the proton transfer in electronic ground and excited states

The potential energy curves were studied for the proton transfer in the ele ctronic ground and excited states for the model systems H3O2-, H4O2, and H5 O2+. The complete active space self-consistent-field calculations were perf ormed for the ground state optimized structures. The potential energy curve s for the proton transfer in the excited states undergo a dramatic change d ue to the different electronic density distribution as an effect of electro nic excitations. In all cases of the studied excited states, the electron p opulation on the transferred proton is higher compared to that in the groun d state. The total charge of the system greatly influences the potential cu rves. Energy separation between ground and excited states is decreased due to the negative charge of the system and is increased when the studied spec ies are positively charged. The vertical excitations of the complex are sim ilar to those in the monomers, but the proton relaxation leads to significa nt energetical (energy barriers) and structural (H+ position) changes. (C) 2001 American Institute of Physics.