Potential energy surfaces of bound and metastable electron-attached states of N2O characterized by a joint experimental and theoretical study

We report a combined experimental and theoretical investigation of electron scattering from nitrous oxide (N2O). Experimental two-dimensional electron energy loss spectra (EELS) provide information about vibrational states of a molecule and about potential energy surfaces of anionic resonances. This study reports the EELS measured at 2.5-2.6 eV incident energy. The calculations using complex-valued extensions of equation-of-motion coupled-cluster theory (based on the non-Hermitian quantum mechanics) facilitate the assignment of all major EELS features. Our simulations identified two broad and partially overlapping resonances-one of pi* and another of sigma* character-located at similar to 2.8 and 2.3 eV vertically at the equilibrium geometry of the neutral. Due to the Renner-Teller effect, the pi* resonance splits upon bending. The upper state, (2)Pi, remains linear. The lower state mixes with the sigma* configuration, giving rise to the (2)A ' resonance, which becomes strongly stabilized at bent geometries (alpha(NNO) = 134 degrees), resulting in very low adiabatic electron attachment energy. The calculations estimate the electron affinity of N2O to be -0.140 eV. The (2)A ' state is predissociative, with the barrier for the N-O bond dissociation of 0.183 eV. The measured EELS feature sharp vibrational structures at low energy losses, followed by a linear (in logarithmic scale) tail extending to the maximum energy loss. The simulations attribute the sharp features at the low energy loss to the non-resonant excitations and contributions from the cold (2)Pi resonance. The tail is attributed to the vibrationally hot (2)A ' state, and its slope is determined by the excess energy available in this state.