The electronic and vibrational properties of a Au- and Li-related center were investigated by using Fourier-transform spectroscopy, together with uniaxial stresses and magnetic fields. The excitation spectrum exhibited a close similarity to a previously studied Au-pair center in that it consisted of zero-phonon lines which were followed by several relatively-sharp phonon replicas. Transitions to 3 different series were observed and, in all cases, phonon energies of about 59 and 47/cm were deduced for the final and initial stages of the transitions, respectively. A Huang-Rhys factor of about 5.7 was determined. In addition to low-temperature transitions from the initial phonon ground state, transitions from the first and second excited photon states were observed at higher sample temperatures. Uniaxial stress experiments revealed a trigonal symmetry for the center and showed that the initial and final electronic states were orbital singlets. Zeeman experiments showed that the center was non-paramagnetic. It was suggested that the center consisted of 2 nearest-neighbor substitutional Au atoms and an unknown number of interstitial Li ions.

Electronic and vibrational structure of a gold- and lithium-related center in silicon P.Tidlund, M.Kleverman: Physical Review B, 1998, 58[8], 4517-20