The luminescence of the 1026-meV optical center, observed in silicon doped with platinum by implantation, was studied under uniaxial stress. The splitting patterns show a complex behavior, especially for the main directions $〈100〉$ and $〈110〉.$ In the $〈100〉$ direction, nonlinear shifts in energy are seen for some components in addition to changes in the intensities. At liquid-helium temperatures, increasing the stress permits the observation of higher-energy transitions. For this center, a model with trigonal symmetry is proposed in which the system has four excited states, three doubly degenerate and one nondegenerate. The three zero phonon lines of the center correspond to transitions of the type $A\leftrightarrow E$ and are polarized in the plane $\mathrm{XY}$ of the center. The transition involving the nondegenerate excited state is forbidden by the selection rules. The application of uniaxial stress causes interaction between the excited states.

• Received 19 January 2001

DOI:https://doi.org/10.1103/PhysRevB.63.235208