The spectroscopy of xanthione in xanthone: An example of spin-orbit coupling dominated zero-field splitting

The phosphorescence, absorption, and excitation spectra of xanthione in xanthone are presented. The extraordinarily large zero-field splitting found for xanthione is confirmed and shown to be in reasonable agreement with calculations assuming that spin-orbit coupling dominates the splitting. In addition, an unusual crystal site dependence of the oscillator strength in the xanthione lowest singlet state is reported. Along with these results we also report the crystal structure of the host xanthone. © 1981 American Institute of Physics.