Silica samples were implanted at multiple energies with Se and Ge ions
producing implanted layers ~ 2.4 µm in depth starting at ~ 0.5 µm below the
surface. In each case, the concentration of implanted species was ~ 0.05
atomic %. The optical absorption of the samples was measured from 2.7 to 6.5
eV. In all spectra, local maxima at 5.0 eV with shoulders at 5.9 eV were
observed. The spectra have been assumed to be describable as a superposition
of Gaussian absorption bands with mean energies taken from the literature of
4.8, 5.01, 5.17, 5.88, and 7.15 eV. The relative strengths of each of these
bands have been obtained by linear regression. These fits show that
additional bands at 3.7 and 6.4 eV are required to fit the data for the Se
samples, while bands at 5.54 and 6.4 eV are needed to fit the data for the
Ge samples.