Kinetics in Cold Laval Nozzle Expansions: From Atmospheric Chemistry to Oxidation of Biomolecules in the Gas Phase
Bibliographic record
Abstract
New developments and recent applications of pulsed and miniaturised Laval nozzle technology allowing many gas-phase molecular processes to be studied at very low temperatures are highlighted. In the present Minireview we focus on molecular energy transfer and reactions of molecular radicals (e.g. OH) with neutral molecules. We show that with the combination of pulsed laser photolysis and sensitive laser-induced fluorescence detection a large number of fast reactions of radicals with more or less complex neutral molecules can be measured in Laval nozzle expansions nowadays. It is also demonstrated that collisional energy transfer of neutral molecules can be measured via kinetically controlled selective fluorescence (KCSF) excitation down to 58 Kelvin. Finally, we show that even the primary steps in the oxidation of biomolecules or biomolecular building blocks initiated by OH radicals can be followed at low temperatures. The temperature dependence of the measured rate constants is the key for an understanding of the underlying molecular mechanisms and the Laval nozzle expansion provides a unique environment for these measurements. The experimental finding that many reactions between radicals and neutral species can be rapid at low temperatures are discussed in terms of pre-reactive complexes formed in the overall complex forming bimolecular reactions.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".