Laboratory Studies of Ion/Molecule Reactions of Fullerenes: Chemical Derivatization of Fullerenes within Dense Interstellar Clouds and Circumstellar Shells
Bibliographic record
Abstract
We discuss recent experimental results for ion/molecule reactions of ionized and multiply-ionized fullerenes, and of derivatized fullerene ions, with molecules relevant to the chemistry of interstellar clouds and circumstellar envelopes These reactions were studied using a selected-ion flow tube (SIFT) at 294 ± 2 K in helium at a pressure of 0.35 ± 0.01 torr. The present study supplements an earlier discussion on aspects of interstellar fullerene ion chemistry explored by the same technique. Several implications are apparent for the chemical processing of fullerenes in various astrophysical environments. Triply charged fullerene ions, such as C 60 3+ , may be formed under conditions prevailing within dense IS clouds, but their abundance will be very low owing to the large number of loss processes identified for such species. Derivatization of fullerene ions under interstellar or circumstellar conditions is less probable for larger fullerenes than for fullerenes smaller than C 60 . Hydrogenation may severely impede the efficiency of fullerene ion association with polar molecules and small unsaturated molecules, but should not substantially affect the efficiency of addition of radicals or PAHs under these conditions. We discuss prospects for neutralization of ionized fullerene adducts. Four classes of adduct ions are described, differing in their structure and expected neutralization tendencies. Adducts of fullerene ions with interstellar isonitriles, with radicals, and with linear polycyclic aromatic hydrocarbons (PAHs; class 1) are most likely to form derivatized fullerenes on neutralization, while fullerene ion adducts of nitriles, most hydrocarbons (class 3), and nonlinear PAHs (class 4) are most likely to yield the bare fullerene cage upon neutralization. Adducts of ammonia (class 2) appear to have an intermediate probability of surviving neutralization with the functionalizing group(s) intact.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".