Reinvestigation of the aluminum hydride (AlH+ and AlD+) cation radicals by ESR in argon matrices at 4 K: Generation by reactive laser sputtering
Knight, L. B.; Cobranchi, S. T.; Gregory, B. W.; Earl, E. A. Reinvestigation of the aluminum hydride (AlH+ and AlD+) cation radicals by ESR in argon matrices at 4 K: Generation by reactive laser sputtering. J. Chem. Phys. 1987, 86, 3143-3143.
The ESR spectra previously assigned to the AlH+ radical ion (X-€‰ 2Î£) J. Chem. Phys. 7 1, 3991 (1979)] actually belong to the divalent neutral aluminum radical AlHOH whose charge distribution and electronic structure can be described as AlH+OH-ˆ’ with 90% of the unpaired electron on the AlH+ part of the molecule. Reactive laser sputtering and photoionization of AlH(g) were used to generate the AlH+ and AlD+ cation radicals, whose ESR spectra have been observed for the first time. A detailed analysis of the ESR results for argon matrices at 4 K reveal unusually large Alhyperfine interaction (hfi) with A iso and A dip values of 1586(2) and 49(1) MHz, respectively. The H hfi is essentially isotropic with A iso=442(2) MHz. The observed nuclear hyperfineAtensors for Al and H show excellent agreement with a b i n i t i o CI theoretical calculations. The results for AlH+ are compared with the isoelectronic neutral radical MgH, and the similar AlF+ cation radical. The Al hfi is slightly larger in AlD+ relative to AlH+. This interesting isotopic effect is qualitatively explained on the basis of electronic structure dependence on small changes in the bond distance for the two isotopic radicals.
Journal of Chemical Physics