The ground state of NO2 is a bent structure but the Rydberg states are planar, resembling the ground-state potential of the cation, NO2+. Cross-sections of the potential energy surfaces of excited states of NO2 reveal the Rydberg character of the excited states. J. Chem. Phys. 115 ( 2001),10394. See also MQDT files.
Fig. 1 Symmetric bending rossections of potential energy surfaces of electronic states of NO2
The most recent contribution deals with the coherent oscillatory femtosecond dynamics in multichannel photodynamics of NO2: J. Phys. Chem. A 114 (2010) 3157.
Fig. 2: Potential energy curves of the electronic states of NO2 relevant to the 3-photon 400nm excitation, involving different types of geometries.
The calculations show that there are avoided crossings or conical intersections between bound and dissociative excited states of different Rydberg and valence character near 9 eV. Thus an oscillating and predissociating wave packet in a quasibound potential of mixed character may explain the oscillations observed in the total photoelectron yield in the fast channel near 0.88 eV, following the initial 400 nm pump laser three photon excitation of (3 × 3.1 eV ) 9.3 eV total excitation energy.
Three-dimentional cuts of the potential energy surface of the ground state of NO2+ (J. Molec. Struct. (Theochem) 434(1998) 117)
Fig. 3: NO2+ ground state potential energy surface: variation of energy with the bond angle and symmetric variation in the bond length.
Fig. 4: Variation of the ground state energy of NO2+ with variations in the bond lengths for planar geometries.