Predissociation dynamics of N(2)O(+) at the A (2)Sigma(+) state: Three pathways to form NO(+)((1)Sigma(+)) revealed from ion velocity imaging.

The predissociation dynamics of nitrous oxide ion ( N 2 O + ) at its first excited state A Σ 2 + has been investigated with ion velocity imaging by probing the NO + fragments. The parent ion N 2 O + , prepared at the ground state X Π 2 ( 000 ) through ( 3 + 1 ) resonance-enhanced multiphoton ionization (REMPI) of jet-cooled N 2 O molecules at 360.55 nm, was excited to different vibrational levels of the A Σ 2 + state in a wavelength range of 280–320 nm, and then predissociated to form NO + and N fragments. The internal energy distribution of the NO + fragment was determined from its ion velocity images. With the help of potential energy surfaces (PESs) of N 2 O + , three dissociation pathways have been proposed to interpret the three kinds of NO + fragments with different internal state distributions: (1) the A Σ 2 + state couples to a dissociative 1 Σ 4 − state via a bound 1 Π 4 state to form the NO + + N ( S 4 ) channel, where NO + fragment is rotationally hot; (2) the A Σ 2 + state couples to dissociative states Σ 2 − / Δ 2 via the 1 Π 4 state to form the NO + + N ( D 2 ) channel, where NO + fragment is also rotationally hot; (3) the A Σ 2 + state couples to the high energy region of the ground state X Π 2 and then dissociates to form the NO + + N ( D 2 ) channel, where NO + is rotationally cold.