Measurements of the Rate Constant of HO<sub>2</sub> + NO<sub>2</sub> + N<sub>2</sub> → HO<sub>2</sub>NO<sub>2</sub> + N<sub>2</sub> Using Near-Infrared Wavelength-Modulation Spectroscopy and UV−Visible Absorption Spectroscopy
Bibliographic record
Abstract
Rate coefficients for the reaction HO 2 + NO 2 + N 2 → HO 2 NO 2 + N 2 (reaction 1) were measured using simultaneous near-IR and UV spectroscopy from 220 to 298 K and from 45 to 200 Torr. Using the data acquired in the present experiment, the low-pressure and high-pressure limit rate constants for reaction 1 were determined to be k o = (2.1 ± 0.1) × 10 -31 × ( T /300) -(3.1±0.3) cm 6 molecule -2 s -1 and k ∞ = (2.4 ± 0.1) × 10 -12 × ( T /300)) -(1.9±0.5) cm 3 molecule -1 s -1, using the expressions for rate constants adopted by the NASA data evaluation panel ( F c = 0.6). The reaction rate was significantly enhanced in the presence of methanol due to a chaperone effect involving an HO 2 ·CH 3 OH complex. Enhancement parameters for this process were quantified as a function of temperature. During the course of our studies, we observed an unexpected time-dependent UV absorption unaccounted for in previous examinations of reaction 1 that employed UV spectroscopy to monitor HO 2 . We show that this absorption, which may have led to errors in those prior studies, is due to the process NO 2 + NO 2 ⇄ N 2 O 4 (reaction 3). Using UV−visible spectroscopy, we determine k - 3 to be (36 ± 10) s -1 at 231 K and 100 Torr using the NASA-recommended equilibrium constant for the dimerization of NO 2 . This represents the first measurement of k - 3 at T < 250 K.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| 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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".