The kinetics of photoinduced defect formation in high-purity silicas has been studied by femtosecond transient absorption spectroscopy in the visible and ultraviolet. Band edge two-photon excitation produces singlet excitons which decay in 0.25 ps into defects with the absorption spectra of nonbridging oxygen hole centers (≡Si-O⋅) and silicon E’ centers (≡Si⋅). We identify these defect pairs with the self-trapped triplet exciton and the 0.25 ps decay with the motion of the photoexcited oxygen atom. Similar results were obtained with both crystalline and amorphous silica samples.
© 1993 American Physical Society
“Primary relaxation processes at the bandedge of SiO_2 ,” P. N. Saeta and B. I. Greene, Phys. Rev. Lett. 70, 3588 (1993). doi: 10.1103/PhysRevLett.70.3588