Cannizzo, A.Leone, M.Gawelda, W.Portuondo-Campa, E.Callegari, A.van Mourik, F.Chergui, M.2009-03-182009-03-182009-03-18200810.1063/1.2975965https://infoscience.epfl.ch/handle/20.500.14299/36200WOS:00025979700006713392The authors studied ultrafast relaxation of localized excited states at Ge-related O deficient centers in SiO2 using femtosecond transient-absorption spectroscopy. The relaxation dynamics exhibits a biexponential decay, which the authors ascribe to the departure from the Frank-Condon region of the 1st excited singlet state in 240 fs, followed by cooling in .apprx.10 ps. At later times, a nonexponential relaxation spanning up to 40 ns occurs, which is fitted with an inhomogeneous distribution of nonradiative relaxation rates, following a chi-square distribution with one degree of freedom. This reveals several analogies with phenomena such as neutron reactions, quantum dot blinking, or intramol. vibrational redistribution. (c) 2008 American Institute of Physics.Excited state (localized; relaxation processes of point defects in vitreous silica from femtosecond to nanoseconds); Excited singlet state; Localized electronic state; Point defects; Vibrational relaxation (relaxation processes of point defects in vitreous silica from femtosecond to nanoseconds); Optical absorption (transient; relaxation processes of point defects in vitreous silica from femtosecond to nanoseconds)relaxation point defect vitreous silica nanosecondtext::journal::journal article::research article