PRODUCT BRANCHING AND LOW TEMPERATURE REACTION KINETICS BY CHIRPED-PULSE FOURIER TRANSFORM MM-WAVE SPECTROSCOPY IN A PULSED UNIFORM SUPERSONIC FLOW
Bibliographic record
Abstract
The CRESU technique (French acronym for “reaction kinetics in uniform supersonic flows”) has been applied with great success in the past two decades to study the kinetics of reactions at low temperatures. In this approach, a uniform low temperature flow is produced via a Laval nozzle expansion giving a wall-less reactor at constant pressure and low temperature. Product detection in that work has been either with laser-induced fluorescence directly in the flow or vacuum ultraviolet photoionization after sampling. We have recently combined low temperature Laval flows with broadband mm-wave detection (chirped-pulse/uniform flow or “CPUF”) to study product branching in photodissociation and reaction.\\footnote{Oldham, J. M.; Abeysekera, C.; Joalland, B.; Zack, L. N.; Prozument, K.; Sims, I. R.; Park, G. B.; Field, R. W.; Suits, A. G. 2014, 141, 154202} Because chirped-pulse microwave detection requires monitoring the free induction decay on the timescale of microseconds, it cannot be employed at the high densities we achieve in the flows. We have used two approaches to overcome this limitation. In one, we used a “quasi-uniform” flow in which an unoptimized Laval flow was followed by a second expansion to lower temperature and density.\\footnote{Dias, N.; Joalland, B.; Ariyasingha, N. M.; Suits, A. G.; Broderick, B. M. The Journal of Physical Chemistry A 2018, 122, 7523-7531.}\\footnote{Broderick, B. M.; Suas-David, N.; Dias, N.; Suits, A. G. Physical Chemistry Chemical Physics 2018, 20, 5517-5529.} Detailed fluid dynamics simulations allow us to understand the temperature and density throughout that flow. Product branching can be measured under these conditions but not kinetics, as the conditions vary throughout the flow. Recently we have implemented airfoil sampling\\footnote{Soorkia, S.; Liu, C.-L.; Savee, J. D.; Ferrell, S. J.; Leone, S. R.; Wilson, K. R. Review of Scientific Instruments 2011, 82, 124102.} of an optimized flow. This allows us to study low temperature kinetics as in CRESU, but with the power of broadband mm-wave spectroscopy. Recent results for several systems relevant to chemistry in cold molecular clouds and planetary atmospheres will be presented using both the quasi-uniform flow and airfoil sampling.
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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 | 0.000 | 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 | 0.001 |
| 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".