The study of the influence of Jahn-Teller coupling and low symmetry strainon the anomalous electron paramagnetic resonance spectrum of titanium(III)doped CsAl(SO4)(2)center dot 12H(2)O

The controversial EPR spectrum of titanium(III) as an impurity in cesium al uminum sulphate alum has been re-examined using conventional CW- and a nove l pulsed-EPR technique, which monitors the nutation frequency as a function of field. The CW-spectra display a high degree of structure, which is inte rpreted as arising from chemically distinct titanium(III) species. The two- dimensional nutation spectrum maps the g(parallel to) vs g(perpendicular to ) relation from just one crystal orientation, and to far greater precision than available from CW-EPR. This novel technique shows that the origin of t he linewidths observed for some of the EPR lines is inhomogeneous broadenin g, the nature of which can be described adequately only in the two-dimensio nal nutation spectrum. Calculations of g(parallel to) vs g(perpendicular to ) have been undertaken by numerical diagonalization of the vibronic Hamilto nian. It is found that the relationship between g(parallel to) and g(perpen dicular to) can be modeled only by assuming that the titanium(III) ions are subject to both dynamic Jahn-Teller coupling and low symmetry strain. Furt hermore, it is shown that the calculated g(parallel to) vs g(perpendicular to) relation is strongly dependent upon the nature of the vibronic interact ion assumed. An excellent reproduction of the experimental data is obtained , using parameters consistent with those employed to model the susceptibili ty data of the isostructural cesium titanium sulphate alum. (C) 2000 Americ an Institute of Physics. [S0021-9606(00)02832-4].