Polarization of luminescence and site symmetry of the Xe center in diamond

We report on polarized photoluminescence studies of the Xe ion-related optical center in diamond. The sample was a single crystal CVD diamond film grown along the (0 0 1) crystallographic plane. The film was irradiated with 180 keV Xe+ ions at room temperature at a dose 5×1012 cm−2 and annealed at 1400 °C. The emission of the sample with laser excitation at 647 nm exhibits the first and second order Raman spectra of diamond, a broad band due to the phonon sideband of the GR1 center, and the Xe center-related features: two zero phonon lines at 813 nm and at 794 nm and a respective vibrational sideband. The Huang-Rhys factor for the Xe center was estimated to be exp(−S)=0.3 at room temperature. The polarization of the Xe center photoluminescence was studied as a function of the sample rotation. The center was established to be a 〈1 1 1〉 oriented defect with a circular dipole absorption transition at 647 nm, a circular dipole emission transition at 794 nm, and a linear dipole emission transition at 813 nm. Possible models of the center were discussed.