Electron spin resonance and theoretical studies of the 14 Nâ â â â 14N and 15Nâ â â â 15N spin-pair radicals in neon matrices: The effects of mixing among the 1Î£+g,3Î£+u,5Î£+g,7Î£+u electronic states
Knight, L. B.; Bell, B. A.; Cobranchi, D. P.; Davidson, E. R. Electron spin resonance and theoretical studies of the 14 Nâ â â â 14N and 15Nâ â â â 15N spin-pair radicals in neon matrices: The effects of mixing among the 1Î£+g,3Î£+u,5Î£+g,7Î£+u electronic states. J. Chem. Phys. 1999, 111, 3145-3145.
The first experimental and theoretical study of the N-‹…-‹…-‹…-‹…N spin-pair radical is reported. Its high-resolution ESR(electron spin resonance)spectrum has been observed in neon matrices and interpreted on the basis of weakly interacting atoms using a model recently developed for the H-‹…-‹…-‹…-‹…H spin-pair. To fully interpret the N-‹…-‹…-‹…-‹…N radical results it was necessary to include electronic state mixing effects among all possible spin states, namely the 1 Î£ g + , 3 Î£ u + , 5 Î£ g + , and 7 Î£ u + states. Several different trapping sites were observed which indicated the interaction of N atoms at distinctly different separation distances in the neon lattice. Calculated J values at the complete active space self-consistent field (CASSCF) level (TZP basis set) were compared with the experimental results for the various trapping site distances. The 15 N-‹…-‹…-‹…-‹… 15 N radical in the dominant trapping site had magnetic parameters of g=2.0016(2), A( 15 N )=15.9(1)-€Š MHz , D=-ˆ’178(1) MHz and J=468(2)-€Š MHz . Using the point dipole approximation this corresponds to a N-‹…-‹…-‹…-‹…N separation distance of 6.41 Ã…. A most unusual type of magnetic dipole transition was observed that involves a transition between electronic states of formally different S values where S is the total spin quantum number for a given electronic state.
Journal of Chemical Physics