  Magnetic resonance in ordered state is shown to be the direct method for
distinguishing the orbital ground state. The example of perovskite titanates,
particularly, LaTiO3 and YTiO3, is considered. External magnetic field
resonance spectra of these crystals reveal glaring qualitative dependence on
assumed orbital state of the compounds: orbital liquid or static orbital
structure. Theoretical basis for using the method as an orbital state probe is
grounded.
