The (A)over-tilde <-(X)over-tilde(1+1)REMPI spectrum and high-level ab initio calculations of the complex between NO and N-2

The results of two separate studies of the complex between NO and N-2 are r eported. The (1+1) REMPI spectrum of the (A) over tilde <--(X) over tilde t ransition of the complex between NO and N-2 is presented of improved qualit y over that reported previously, and the appearance of the spectrum is disc ussed. The results of high-level ab initio calculations [RCCSD(T)/aug-cc-pV QZ//QCISD/6-311+G(2d)] on the (X) over tilde (2)Pi state are also reported. The indications are that the NO moiety is more freely rotating in the comp lex than is N-2, and that a wide angular space is sampled in the zero-point energy level. The appearance of the REMPI spectrum suggests that the (A) o ver tilde (2)Sigma (+) state is (close to) linear, and RCCSD(T)//QCISD calc ulations on the (A) over tilde state, using Rydberg-function-augmented basi s sets, suggest that the lowest energy linear isomer is the ON .N-2 linear orientation. It is clear, however, that the understanding of this complex, and its spectroscopy, is far from complete, and will be challenging. (C) 20 00 American Institute of Physics. [S0021-9606(00)00548-1].