Using an ab initio methodology, we compute the potential energy curves and the spinorbit coupling integrals of the N 2 electronic states located in the 0-120000 cm -1 energy domaine.In our analysis, we focus mostly on those located outside the Franck-Condon regio n accessible from the ground state of N 2 i.e. the two strongly bound states 1 3 Σ g -and 1 1 Γ g , and the weakly bound state 2 3 Σ g -, in addition to several repulsive states. We characterize them spectroscopically and we compute their spin-orbit couplings to the close lying singlets, triplets and quintets. This work completes our knowledge on the electronic states of N 2 that may be important intermediates during N + N collisions and for the dynamics of the N 2 singlets and triplets and quintets VUV photodissociation.

The branching ratios for the N(4 S) + N(2 D), N(4 S) + N(2 P), and N(2 D) + N(2 D) channels are measured for the photodissociation of X v J N ; 0, g 2 1 () S  =  + in the vacuum ultraviolet (VUV) region of 100,808-122,159 cm −1 using theVUV-VUV pump-probe approach combined with velocity-map-imaging-photoion detection. No evidence of forming the ground-state N(4 S) + N(4 S) products is found. No potential barrier is observed for the N (2 D) + N(2 D) channel, but the N(4 S) + N(2 P) channel has a small potential barrier of ≈740 cm −1. The branching ratios are found to depend on the symmetry of predissociative N 2 states instead of the total VUV excitation energy, indicating that N 2 photodissociation is nonstatistical. When the branching ratios for N(4 S) + N(2 D) and N(4 S) + N (2 P) products are plotted as a function of the VUV excitation energy for the valence N 2 1 Π u and 1 u S + states, oscillations in these ratios are observed demonstrating how these channels are competing with each other. These data can be used to select both the velocity and internal states of the atomic products by picking the quantum state that is excited. High-level ab initio potential energy curves of the excited N 2 states are calculated to provide insight into the mechanisms for the observed branching ratios. The calculations predict that the formation of both N(4 S) + N(2 D) and N(4 S) + N(2 P) channels involves potential energy barriers, in agreement with experimental observations. A discussion of the application of the present results to astronomy, planetary sciences, and comets is given.

Large calculations are done to investigate the valence and inner-valence electronic states of aluminum monochloride and its cationic species AlCl+ and AlCl2+, allowing their definite assignment. This concerns particularly the computations of the potential-energy curves of the electronic states of these species and their spin-orbit couplings and transition moments. An accurate set of spectroscopic constants for these species is also deduced. For the neutral molecule, our calculations show that the lifetimes of the AlCl A1pi v' > or = 10 levels are reduced to the 0.1-0.01 ps time scale because of spin-orbit induced predissociation processes and by tunneling through the potential barrier of the A state. Our potential curves for the ground state of AlCl and those of the cationic and dicationic species are also used for predicting the single and double ionization spectrum of AlCl. For both the cation and the dication, long-lived rovibrational levels are predicted.