Dissociation of the Anthracene Radical Cation: A Comparative Look at iPEPICO and Collision-Induced Dissociation Mass Spectrometry Results
Bibliographic record
Abstract
The dissociation of the anthracene radical cation has been studied using two different methods: imaging photoelectron photoion coincidence spectrometry (iPEPCO) and atmospheric pressure chemical ionization-collision induced dissociation mass spectrometry (APCI-CID). Four reactions were investigated: (R1) C14H10(+•) → C14H9(+) + H, (R2) C14H9(+) → C14H8(+•) + H, (R3) C14H10(+•) → C12H8(+•) + C2H2 and (R4) C14H10(+•) → C10H8(+•) + C4H2. An attempt was made to assign structures to each fragment ion, and although there is still room for debate whether for the C12H8(+•) fragment ion is a cyclobuta[b]naphthalene or a biphenylene cation, our modeling results and calculations appear to suggest the more likely structure is cyclobuta[b]naphthalene. The results from the iPEPICO fitting of the dissociation of ionized anthracene are E0 = 4.28 ± 0.30 eV (R1), 2.71 ± 0.20 eV (R2), and 4.20 ± 0.30 eV (average of reaction R3) whereas the Δ(‡)S values (in J K(-1) mol(-1)) are 12 ± 15 (R1), 0 ± 15 (R2), and either 7 ± 10 (using cyclobuta[b]naphthalene ion fragment in reaction R3) or 22 ± 10 (using the biphenylene ion fragment in reaction R3). Modeling of the APCI-CID breakdown diagrams required an estimate of the postcollision internal energy distribution, which was arbitrarily assumed to correspond to a Boltzmann distribution in this study. One goal of this work was to determine if this assumption yields satisfactory energetics in agreement with the more constrained and theoretically vetted iPEPICO results. In the end, it did, with the APCI-CID results being similar.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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 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".