Abstract
The fluorescence and excitation spectra of in the ordered and disordered phases of the spinel Li have been measured at 77 and 4.2 K. At these temperatures, a strong zero-phonon line is observed in the ordered-phase fluorescence accompanied by relatively well-defined vibronic sidebands. These sidebands are separated by a common frequency interval of 199 . Their origin is attributed to local modes of an [Fe] center. Several large splittings are observed. A splitting of approximately 600 is seen in the and levels at the tetrahedral sites. A splitting of 16 seen in the zero-phonon line is believed due to spin-orbit effects. Good agreement is obtained between calculated and observed level positions. Our earlier suggestion that the fluorescence of the ordered phase is due to at tetrahedral () sites while the fluorescence of the disordered phase is due to at octahedral () sites is strengthened. Finally, we present a comparison of certain basic features of Li: obtained from optical measurements with those obtained from Mössbauer-effect measurements. The latter will be published separately.
- Received 17 June 1971
DOI:https://doi.org/10.1103/PhysRevB.5.3377
©1972 American Physical Society