Spectroscopy and picosecond dynamics of aqueous NO2

We investigate the formation of aqueous nitrogen dioxide, NO2 formed through femtosecond photolysis of nitrate, ${\rm NO}_{\rm 3}^ - \left( {aq} \right)$ NO 3−aq and nitromethane CH3NO2(aq). Common to the experiments is the observation of a strong induced absorption at 1610 ± 10 cm−1, assigned to the asymmetric stretch vibration in the ground state of NO2. This assignment is substantiated through isotope experiments substituting 14N by 15N, experiments at different pH values, and by theoretical calculations and simulations of NO2–D2O clusters.