Isotope Effect on the Infrared Photoluminescence Decay of Interstitial Oxygen Molecules in Amorphous SiO₂

Abstract

The decay constants of the a1Δg(v=0)→X3Σg-(v=0) infrared photoluminescence (PL) of isotopically-labeled oxygen molecules 16O18O and 18O2 dissolved in the interstitial voids of a-SiO2 are ∼1.7 and ∼2.5 times larger than that of 16O2. This difference originates from the isotope shift in the energy of the nonradiative transitions from the a state to the vibronic levels of the X ground state. Calibration of the PL quantum yield using the measured decay constants is essential to measure the correct concentration of isotopically-labeled interstitial O2.

Oxygen-excess amorphous SiO2 with 18O-labeled interstitial oxygen molecules

“…Purely electronic band (PEB) located at ~7855 cm − 1 and a vibrational sideband (VSB), which is separated from PEB by the energy of the O-O stretching mode, were identified [19]. The peak position of VSB was almost identical to the position expected for interstitial 18 O 2 , indicating that the fraction of interstitial 18 O 2 (f 88 ) is much larger than that of interstitial 16 [20]. The peak decomposition shown in the inset yielded f 66 ≃ 0.05, f 68 ≃ 0.11, and f 88 ≃ 0.84, confirming that the fraction of 18 O atoms in interstitial O 2 (f * ≡ f 88 + f 86 /2) was as large as 90% (~0.89).…”

“…This tube was thermally annealed for 1500 h at 500°C to incorporate 18 O-labeled O 2 into the specimens. Interstitial O 2 in a-SiO 2 was measured by infrared photoluminescence (PL) [19,20]. A continuouswave AlGaAs laser diode operated at 765 nm (~1.5 W at sample position) was used as a PL excitation source.…”

“…The peak decomposition shown in the inset yielded f 66 ≃ 0.05, f 68 ≃ 0.11, and f 88 ≃ 0.84, confirming that the fraction of 18 O atoms in interstitial O 2 (f * ≡ f 88 + f 86 /2) was as large as 90% (~0.89). The thickness average of total interstitial O 2 concentration (C a T ) evaluated from the PEB intensity [20] was~3.8 × 10 17 cm − 3 .…”

Exchange between interstitial oxygen molecules and network oxygen atoms in amorphousSiO2studied byO18Kajihara1, Miura2, Kamioka3 et al. 2011Phys. Rev. BSelf Cite90110View full textAdd to dashboardCite

“…18,22 However, a correction due to changing fractions of interstitial 16 18 O 2 (τ 66 < τ 68 < τ 88 ), and τ is proportional to the PL quantum yield of the PEB. 23 Thus, the variation of the "effective" PL quantum yield with the fractions of 18 O-labeled interstitial O 2 was accounted for by multiplying the observed PEB intensity by a factor f 66 τ 66 /(f 66 τ 66 + f 68 τ 68 + f 88 τ 88 ). f 66 , f 68 , and f 88 were evaluated by simple peak decomposition of the VSB spectrum using three pseudo-Voigt peak functions with peak parameters that were predetermined, as described in Refs.…”

Photoluminescence and diffusion properties of O2 molecules in amorphous SiO2 nanoparticles

“…This process adds to the already observed radiative and non radiative decay processes in bulk silica materials. The latter, in particular, has been associated to coupling of O 2 with high energy vibrational modes of the silica matrix or of impurity defects that cannot be activated up to room temperature due to their high energy [12,13]. By contrast, the additional thermally activated decay should be associated to low activation energy processes due to degrees of freedom of oxygen molecule and interaction with neighbouring matrix.…”