Theoretical study of fine and hyperfine interactions in N3+, N3•, and N3-

The geometries and the harmonic vibrational frequencies have been computed for the N-3(+)((X) over tilde (3)Sigma(g)(-),a (1)Delta(g),(b) over tilde (1)Sigma(g)(+),(A) over tilde (3)Pi(u),1 (1)Pi(u)), N-3(.-)((X) over tilde (2)Pi(g),(A) over tilde (2)Sigma(u)(+),1 (2)Sigma(g)(+)), and N-3(-)((X) over tilde (1)Sigma(g)(+)) systems using the full-valence complete active space self-consistent-field (CASSCF) vectors. The systems N-3(+)((A) over tilde (3)Pi(u),1 (1)Pi(u)) and N-3(.)((X) over tilde (2)Pi(g)) possess two distinct real frequencies for the bending modes. The energy for both components increases upon bending and these states are subject to the type A Renner-Teller effect. The energetics and the dynamical properties have been studied at the complete active space second order perturbation theory (CASPT2) and the multireference singles and doubles configuration interaction (MRSD-CI) levels of theory. The spin-orbit coupling constants, A(SO) in N-3(+)((A) over tilde (3)Pi(u)) and N-3(.)((X) over tilde (2)Pi(g)) are obtained by employing the atomic mean field spin-orbit Hamiltonian and these are about 3 cm(-1) from the experiment. The nuclear quadrupole coupling constants at various nitrogen centers have been predicted in all the systems by employing the CASSCF, the CASPT2 and the MRSD-CI-ino (iterative natural orbital procedure) methods. The magnetic hyperfine coupling constants (hfcc's) have been computed for the various N-14's in N-3(+)((X) over tilde (3)Sigma(g)(-),(A) over tilde (3)Pi(u)) and N-3(.)((X) over tilde (2)Pi(g),(A) over tilde (2)Sigma(u)(+),1 (2)Sigma(g)(+)) at the configuration selected MRSD-CI-ino level of theory using weighted threshold criteria for the configuration selection. (C) 2003 American Institute of Physics.