ELECTRON-SPIN-RESONANCE STUDIES OF THE TITANIUM CATION (TI-4) IN RARE-GAS MATRICES AT 4 K - A CRYSTAL-FIELD INTERPRETATION(,3D(3),F)

Electron-spin resonance studies of laser-ablated titanium metal isolat ed in neon and argon display an intense feature which exhibits a symme tric, narrow line and a large matrix-dependent g shift. On the basis o f a number of experiments, this is assigned to a matrix isolated 3d(3) ,F-4 Ti+ ion in an octahedral matrix environment. Although the ground state of the gas-phase Ti+ ion is 3d(2)4s(1),F-4, the assignment to th e 3d(3),F-4 State is supported by the small hyperfine structure which is observed. The neon magnetic parameters are: g=1.934(1) and A (Ti-47 )=64(1) MHz; for argon, g=1.972(1) and A=56(1) MHz. This unusual stabi lization of an excited atomic state by a rare gas matrix is consistent with ab initio studies, and has been previously found for atomic nick el. A crystal-field study of the expected behavior of a d(3),F-4 ion i solated in a tetrahedral, octahedral, or cuboctahedral environment sup ports the assignment to an octahedral Ti+(Rg)(6) species, and using th e atomic spin-orbit parameter, zeta permits accurate values of Dq to b e derived from the measured g values. Finally, it is also noted that f or small values of Dq/(Dq+zeta), or for a d(3),F-4 ion in a tetrahedra l environment, an as yet unobserved, unequal Zeeman splitting of the f ourfold degeneracy occurs, causing a departure of the Zeeman energies from the standard formula of E(Zeeman)=beta(e)H(0)gM, with M = +/-3/2, +/-1/2. For these situations it becomes necessary to define two value s of g, corresponding to the more strongly (g(3/2) and less strongly ( g(1/2)) affected Zeeman levels, respectively. (C) 1996 American Instit ute of Physics.