Optical lasing during laser filamentation in the nitrogen molecular ion: Ro-vibrational inversion
Bibliographic record
Abstract
Summary form only given. Inducing and controlling lasing in the open air is an intriguing challenge. Several recent experiments on laser filamentation in air have demonstrated generation of population inversion and lasing at the 391 nm and 428 nm lines in the nitrogen molecular ion [1-8], corresponding to transitions between the ground vibrational state of the second excited electronic state, B2Σu+, and the ground and first excited vibrational state of the ground electronic state, X2Σg+, see figure. Importantly, lasing at these transitions appears to be a very general effect, arising during filamentation of virtually any incident radiation, from visible to mid-infrared. We propose a mechanism that explains the population inversion between the B2Σ+u and X2Σ+gstates based on the combined effect of several processes: (i) tunnel ionization of the neutral nitrogen molecule to the different relevant ionic states, using numerically calculated, angular-resolved strong-field ionization rates, (ii) laser-induced ultrafast electronic excitations in the ion, (iii) molecular vibrations, (iv) alignment of the molecule induced by the strong laser pulse, and (v) molecular rotation upon ionization.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.009 | 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".