  The photodissociation dynamics of N$_3^+$ excited from its $^3 \Sigma_{\rm
g}^{-}$ 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 $^1 \Delta_{\rm g}$ and $^3
\Pi_{\rm u}$ 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.
