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Photodissociation dynamics of N$_{3}^{+}$

The photodissociation dynamics of N$_3^+$ excited from its $^3 Σ_{\rm g}^{-}$ ground to the first excited singlet and triplet states is investigated. Three dimensional potential energy surfaces for the $^1$A$'$, $^1$A$''$, and $^3$A$'$ electronic states, correlating with the $^1 Δ_{\rm g}$ and $^3 Π_{\rm u}$ states in linear geometry, for N$_3^+$ are constructed using high level electronic structure calculations and represented as reproducing kernels. The reference {\it 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 N$_2$ product are determined from vertically excited ground state distributions. Due to the different shapes of the ground state $^3$A$^{''}$ PES and the excited states, appreciable angular momentum $j' \sim 60$ is generated in the 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.