Electron-spin resonance studies of laser-ablated titanium metal isolated in neon and argon display an intense feature which exhibits a symmetric, narrow line and a large matrix-dependent g shift. On the basis of a number of experiments, this is assigned to a matrix isolated 3d 3 , 4 F Ti ϩ ion in an octahedral matrix environment. Although the ground state of the gas-phase Ti ϩ ion is 3d 2 4s 1 , 4 F, the assignment to the 3d 3 , 4 F state is supported by the small hyperfine structure which is

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... served. The neon magnetic parameters are: gϭ1.934͑1͒ and A͑ 47 Ti͒ϭ64͑1͒ MHz; for argon, gϭ1.972͑1͒ and Aϭ56͑1͒ MHz. This unusual stabilization of an excited atomic state by a rare gas matrix is consistent with ab initio studies, and has been previously found for atomic nickel. A crystal-field study of the expected behavior of a d 3 , 4 F ion isolated in a tetrahedral, octahedral, or cuboctahedral environment supports the assignment to an octahedral Ti ϩ ͑Rg͒ 6 species, and using the atomic spin-orbit parameter, permits accurate values of Dq to be derived from the measured g values. Finally, it is also noted that for small values of Dq/(Dqϩ), or for a d 3 , 4 F ion in a tetrahedral environment, an as yet unobserved, unequal Zeeman splitting of the fourfold degeneracy occurs, causing a departure of the Zeeman energies from the standard formula of E Zeeman ϭ␤ e H 0 gM, with M ϭϮ3/2, Ϯ1/2. For these situations it becomes necessary to define two values of g, corresponding to the more strongly ͑g 3/2 ͒ and less strongly ͑g 1/2 ͒ affected Zeeman levels, respectively.