Characterization of the electronic states of the biological relevant SSNO molecule.

Using configuration interaction ab initio methods, we investigate the lowest electronic states of doublet and quartet spin multiplicities of SSNO where the one-dimensional cuts of the six-dimensional potential energy surfaces of these electronic states along the stretching and bending coordinates are computed. Mainly, these electronic states are found to be repulsive along the central SN distance. A high density of electronic states is computed even at low excitation energies that may favor their couplings. Therefore, the dynamics of the SSNO electronic states is expected to be very complex. We also characterized the bound electronic states spectroscopically where we derived their equilibrium structures and vibrational frequencies. Our calculations show the importance of taking into account of dynamical correlation, in addition to static correlation, for the accurate description of SSNO electronic excited states and more generally for those of R-NO molecular species. Finally, we highlighted the potential role of SSNO in light-induced NO delivery from SSNO related species in biological media.