The flowstone contains uranium, which over time decays
This can explain the increase of time decays in the Urbach tail condition.
Figure 8 summarizes our results: (i) for excitation above bandgap, the photoconductivity time decays <[tau]> (Figure 8(a)) are longer when the presence of oxygen or an overpressure in atmosphere is decreased while the photoresponse increases in the absence of oxygen (Figure 8(b)).
The increase of photoconductivity time decays when excited below bandgap is attributed to the mitigation of oxygen photodesorption.
In the current case a YAG:Eu based phosphor was used with 532nm excitation wavelength to achieve short life time decays at low temperatures.
Hence the current probe design enables the observation of the undistorted life time decay. Figure 4 shows the variation in intensity of a constant light source when moving across the field of view (FOV) of the OPETS.
Several publications have shown the dependency between the life time decay of this phosphorescence and the temperature [5,7-11,15,16].
10) to effect a layered metaphor: Time decays
or sullies the fine clothes of youth, changing bright to dark.
, remakes, transfigures them; they become painful vessels of memory, touchstones of experience.
The two observed fast time decays [[tau].sub.2] and [[tau].sub.3] in dyes-Ti[O.sub.2] systems could be also attributable to a contemporary presence of different injection processes; due to different possible configurations of ZnPc molecules when they are interacting with Ti[O.sub.2] surface, one is more favourable than the other.
The longer decay is comparable with time decay reported in the literature for N719 systems , while the shorter excited-state lifetime indicates an enhancing of the nonradiative deactivation channels, probably due to the presence of protons on carboxyl groups .
The faster time decay component in dye-Ti[O.sub.2] system ([[tau].sub.3]) could be, in principle, indicative of an efficient injection occurring at the interface between dye molecules and semiconductor surface.