A comparison is made of the phonon spectra of several rare earth aluminum garnet crystals. The conclusion drawn is that the Raman Spectra with shifts >400 em -1 can be interpreted in terms of motions associated with A104-tetrahedrons of symmetry S 4. Phonon modes associated with the movements of the rare earth ions could also be assigned and the frequency dependence of these modes could be correlated to the apparent change in environment of the rare earth ions in the aluminum garnet crystals when the radii of the ions decrease.

No abstract

The low temperature laser excited Raman spectrum of the compound thulium gallium garnet reveals the presence of an electronic transition of the thulium ion. The tensor associated with this transition can contain some asymmetry. Polarization measurements show, however, that the amount of asymmetry is too small to be detectable.

No abstract

The amplitude for the decay X0 --I 2my is constructed using a finite dispersion relation. The decay width and distribution are found to be consistent with recent experiment. A finite-energy sum rule analysis indicates that the coupling of the X0 to the photon and the p meson, g,,~, has its quark-model value. A similar study is made of q 1 2 m y from which it is concluded that g , , , probably also has its quark-model value.