IDENTIFICATION OF H<sub>2</sub>CCC AS A DIFFUSE INTERSTELLAR BAND CARRIER
Bibliographic record
Abstract
We present strong evidence that the broad, diffuse interstellar bands (DIBs) at 4881 and 5450 Å are caused by the B 1 B 1 ← X 1 A 1 transition of H 2 CCC ( l -C 3 H 2 ). The large widths of the bands are due to the short lifetime of the B 1 B 1 electronic state. The bands are predicted from absorption measurements in a neon matrix and observed by cavity ring-down in the gas phase and show exact matches to the profiles and wavelengths of the two broad DIBs. The strength of the 5450 Å DIB leads to a l -C 3 H 2 column density of ∼5 × 10 14 cm −2 toward HD 183143 and ∼2 × 10 14 cm −2 to HD 206267. Despite similar values of E ( B − V ), the 4881 and 5450 Å DIBs in HD 204827 are less than one-third their strength in HD 183143, while the column density of interstellar C 3 is unusually high for HD 204827 but undetectable for HD 183143. This can be understood if C 3 has been depleted by hydrogenation to species such as l -C 3 H 2 toward HD 183143. There are also three rotationally resolved sets of triplets of l -C 3 H 2 in the 6150–6330 Å region. Simulations, based on the derived spectroscopic constants and convolved with the expected instrumental and interstellar line broadening, show credible coincidences with sharp, weak DIBs for the two observable sets of triplets. The region of the third set is too obscured by the α-band of telluric O 2 .
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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) | 0.003 | 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".