Dissociative recombination slows the expansion of a molecular ultracold plasma
Bibliographic record
Abstract
A fluid model for the expansion of a molecular ultracold plasma composed of NO${}^{+}$ ions and electrons shows that fast dissociative recombination (DR) flattens the charged-particle density distribution, effectively freezing the expansion of the plasma core. However, a much greater fraction of the plasma mass exists at lower density in the wings of the plasma, where dissociative recombination has little effect, and ion motion is driven by a Gaussian charge-density gradient. Here, expansion proceeds as the collisionless acceleration of the ions under the radial pressure of the expanding electron gas. Even though DR flattening dramatically suppresses the radial velocity of ions in the densest part of the plasma, the measured evolution of the overall plasma width remains dominated by the expansion of the outer shells. Thus, despite its frozen core, a dissociating plasma with an initial electron temperature ${T}_{e}(0)$ exhibits a time-evolving width that differs only slightly from a Vlasov expansion with the same ${T}_{e}(0)$.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".