ESR and ab initio theoretical studies of the cation radicals14N+4 and 15N+4 The trapping of ion-neutral reaction products in neon matrices at 4 K
Knight, L. B.; Johannessen, K. D.; Cobranchi, D. C.; Earl, E. A.; Feller, D.; Davidson, E. R. ESR and ab initio theoretical studies of the cation radicals14N+4 and 15N+4 The trapping of ion-neutral reaction products in neon matrices at 4 K. J. Chem. Phys. 1987, 87, 885-885.
The 1 4N+ 4 and 1 5N+ 4 molecular cation radicals have been generated by the ion-€“neutral reaction N+ 2 +N2 and isolated in solid neon matrices at 4 K for detailed ESR(electron spin resonance) investigation. Both photonionization at 16.8 eV and electron bombardment (50 eV) were used in conjunction with the neon matrix trapping technique to produce the N+ 4 dimer cation. The ESR results clearly show that N+ 4 is linear and has a 2Î£Î¼ground electronic state. The magnetic parameters in neon are: g -ˆ¥=2.0016(4) and g -Š¥=1.9998(2); A -ˆ¥(1 4N)=311(1) MHz and A -Š¥(1 4N)=264(1) MHz for the central atoms and -€-A -ˆ¥-€-=10.4(5) MHz and -€-A -Š¥-€-=20.4(1) MHz for the outer or terminal 1 4N atoms. Electronic structure information for N+ 4 was obtained from the ESR results and compared with a b i n i t i o CI calculations. The unpaired electron resides primarily on the inner nitrogen atoms with significant 2p Ïƒ and 2s character. Orbital characters obtained from the commonly applied free atom comparison method (FACM) were compared with the results of a Mulliken type spin population analysis conducted on the calculated wave function. The calculated nuclear hyperfine parameters (Atensors) showed reasonable agreement with experiment except for the very small A iso parameter for the outer nitrogen atoms. Benchmark calculations employing large basis sets were conducted for the free nitrogen atom; these efforts demonstrate the difficulty in computing the A iso parameter when inner shell effects are important.
Journal of Chemical Physics