ON THE STRUCTURE AND STABILITY OF GEOMETRICAL-ISOMERS OF N3F

The potential energy surfaces for the N3F molecule have been studied u sing multiconfigurational wave functions. Two new isomers were found, one on the singlet ((1)A') and one on the triplet ((3)A'') surface. Bo th isomers have a three-membered cyclic structure and C-s symmetry. Th e singlet cyclic isomer is endoergic relative to the open fluorine azi de by 15-17 kcal/mol. Its kinetic stability is close to the stability of the open isomer: the barrier separating the cyclic isomer from the dissociation products N-2(X (1) Sigma(g)(+))+NF(a (1) Delta) is about 13-17 kcal/mol and is lower than the barrier to isomerization. The tri plet cyclic isomer is much higher in energy (about 70 kcal/mol), with a barrier to dissociation to N-2(X 1 Sigma(g)(+))+NF(X (3) Sigma(-)) o n the order of 15 kcal/mol. Crossings of the (1)A' and the 3A'' surfac es may allow the cyclic singlet isomer to predissociate to the ground state products, N-2(X (1) Sigma(g)(+))+NF(X (3) Sigma(-)). It is shown , however, that the singlet-triplet surface of intersection lies 'behi nd' the barrier to singlet decomposition,so that spin-forbidden predis sociation will not preclude detection of cyclic N3F. (C) 1995 American Institute of Physics.