Measurements of the Rate Constant of HO_2 + NO_2 + N_2 → HO_2NO_2 + N_2 Using Near-Infrared Wavelength-Modulation Spectroscopy and UV−Visible Absorption Spectroscopy
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Bibliographic record
Abstract
Rate coefficients for the reaction HO_2 + NO_2 + N_2 → HO_2NO_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_3OH 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_2O_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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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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