MAGNETIC CIRCULAR-DICHROISM AND ABSORPTION-SPECTRA OF THE GAMMA-BAND REGION OF TITANIUM MONOXIDE IN AN ARGON MATRIX

Magnetic circular dichroism (MCD) and absorption spectra are reported for the gamma-band region (12 500-19 000 cm(-1)) of TiO in an Ar matri x. The spectra show two sets of transitions that can be assigned to Ti O molecules at inequivalent matrix sites. Sharp absorption bands and t emperature-independent A terms are found to be quantitatively consiste nt, with the 4 pi <-- 6 sigma electronic excitation of randomly orient ed molecules at high-symmetry sites. For the other site(s), which are associated with broad absorption bands and temperature-dependent C ter ms, a model is proposed where ground-state orbital angular momentum is partially quenched by a low-symmetry crystal field. Semiquantitative application of this model explains some of the finer details of the sp ectra and suggests a preferential orientation of the low-symmetry site s where the molecular axis is perpendicular to the surface of the matr ix-deposition window.