Photodissociation dynamics of N₃

The photodissociation dynamics of N₃ ⁺ excited from its (linear) ³Σ_g ^-/(bent) ³A″ ground to the first excited singlet and triplet states is investigated. Three-dimensional potential energy surfaces for the ¹A', ¹A″, and ³A' electronic states, correlating with the ¹Δ_g and ³Π_u states in linear geometry, for N₃ ⁺ are constructed using high-level electronic structure calculations and represented as reproducing kernels. The reference ab initio energies are calculated at the MRCI+Q/aug-cc-pVTZ level of theory. For following the photodissociation dynamics in the excited states, rotational and vibrational distributions P(v') and P(j') for the N₂ product are determined from vertically excited ground state distributions. Due to the different shapes of the ground state ³A″ potential energy surface and the excited states, appreciable angular momentum j' ∼ 60 is generated in diatomic fragments. The lifetimes in the excited states extend to at least 50 ps. Notably, results from sampling initial conditions from a thermal ensemble and from the Wigner distribution of the ground state wavefunction are comparable.