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Mixed nitrogen-lithium cluster cations LiN n + were generated by laser vaporization and analyzed by time-offlight mass spectrometry. It is found that LiN 8 + has the highest ion abundance among the LiN n + ions in the mass spectrum. Density functional calculations were conducted to search for the stable structures of the Li-N clusters. The theoretical results show that the most stable isomers of LiN n + clusters are in the form of Li + (N 2 ) n/2 , and the order of their calculated binding energies is consistent with that of Li-N 2 bond lengths. The most stable structures of LiN n + evolve from one-dimensional linear type (C Nv , n ¼ 2; D Nh , n ¼ 4), to two-dimensional branch type (D 3h , n ¼ 6), then to three-dimensional tetrahedral (T d , n ¼ 8) and square pyramid (C 4v , n ¼ 10) types. Further natural bond orbital analyses show that electrons are transferred from the lone pair on N a of every N 2 unit to the empty orbitals of lithium atom in LiN 2-8 + , while in LiN 10 + , electrons are transferred from the bonding orbital of the Li-N a bonds to the antibonding orbital of the other Li-N a bonds. In both cases, the N 2 units become dipoles and strongly interact with Li + . The average second-order perturbation stabilization energy for LiN 8 + is the highest among the observed LiN n + clusters. For neutral LiN 2-8 clusters, the most stable isomers were also formed by a Li atom and n/2 number of N 2 units, while that of LiN 10 is in the form of Li + (N 2 ) 3 (h 1 -N 4 ).

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