Measurement of the <sup>13</sup>C/<sup>12</sup>C of Atmospheric CH<sub>4</sub> Using Near-Infrared (NIR) Cavity Ring-Down Spectroscopy
Why this work is in the frame
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Bibliographic record
Abstract
A near-infrared (NIR) continuous-wave-cavity ring-down spectrometry (CW-CRDS) device was developed with the goal of measuring seasonal changes in the isotopic composition of atmospheric CH4 on Earth and eventually on Mars. The system consisted of three distributed feedback laser diodes (DFB-LDs), two of which were tuned to the absorption line peaks of (12)CH4 and (13)CH4 at 6046.954 cm(-1) and 6049.121 cm(-1), respectively, and a third that measured the baseline at 6050.766 cm(-1). The multiple laser design improved the long-term stability of the system and increased the data acquisition rate. The acquisition frequency was further increased by utilizing a semiconductor optical amplifier (SOA) to initiate cavity ring-down events. The high repetition rate combined with the superhigh reflectivity mirrors yielded precise isotopic measurements in this NIR region, even though the line strengths of CH4 in this region are 200 times weaker than those of the strongest mid-IR absorption bands. The current system has a detection limit of 1.9 × 10(-12) cm(-1), corresponding to 10 pptv of CH4 at 100 Torr. For ambient air samples that contained 1.9 ppmv CH4, the δ(13)C of the CH4 was determined to be -48.7 ± 1.7‰ (1σ).
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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