Photoinduced Processes in Heterogeneous Gas−Solid Systems. Temperature Dependence (100−600 K) and Modeling of a Surface Chemical Reaction on Zirconia that Triggers Photophysical Events in the Solid
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Bibliographic record
Abstract
We report studies on photoinduced processes that take place in gas−solid heterogeneous systems. In particular, we examine the chemical reaction (i.e., chemical relaxation pathway) between hydrogen (or methane) and the surface of ZrO 2 particles which occurs after the solid was preirradiated (vacuo or oxygen) and the intrinsic phosphorescence from zirconia had terminated. Introduction of H 2 yields an after-glow (light pulse referred as photoinduced chesorluminescence, PhICL) that is caused by chemical interaction between the photoactivated surface of the photocatalyst and the H-containing molecules in the heterogeneous gas−solid system. Unlike hydrogen, methane does not yield a detectable PhICL emission. The PhICL emission for hydrogen decays via biphasic kinetics (τ 1 = 0.9 s and τ 2 = 10 s; ambient temperature). Reactions were also investigated in the temperature range of 75−600 K. For a nonpreirradiated surface, the H-containing molecules physisorb with binding energy E phys = 33 kJ mol -1 (0.34 eV) for H 2 and 52 kJ mol -1 (0.54 eV) for CH 4 . After preirradiation of ZrO 2, the molecules chemisorb dissociatively yielding free radicals (H • for H 2, and CH 3 • for methane, the other H • is trapped) through an activated process; activation energies E a = 30 kJ mol -1 (0.31 eV) for H 2 and 32 kJ mol -1 (0.33 eV) for CH 4 if the process occurs by a Langmuir-type pathway; if the process occurs by an Eley-Rideal mechanism, E a = 41 kJ mol -1 (0.43 eV) for H 2 and 46 kJ mol -1 (0.48 eV) for CH 4 . The data were modeled through a sequence of differential equations. A mechanism is proposed that involves shallow traps and deep energy traps for electrons to explain the photophysical events triggered by the surface chemical reaction. In essence, surface chemical reactions cause the release of the energy stored during the preirradiation stage of the solid. This results in photoinduced formation of metastable defects in the solid (e.g., O s -• ) together with deep electron traps ( F centers) that lead to both chemical and physical relaxation of the system.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it