A Reexamination of the Dissociative Photoionization of Isoprene
Bibliographic record
Abstract
We explore the ionization of isoprene and the unimolecular dissociation chemistry of its radical cation employing imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. The origin band of the threshold photoelectron spectrum (TPES) indicates an ionization energy of 8.87 ± 0.01 eV in agreement with the calculated CBS-QB3 values. Franck–Condon (FC) simulations rationalize the vibrational structure of the ground-state band in the TPES, and Outer Valence Green’s Function calculations for the excited electronic states are compared with the excited-state bands in the TPES. Four major fragment ions were observed at photon energies above 10.5 eV: C 5 H 7 + ( m / z 67, loss of H), C 4 H 5 + ( m / z 53, loss of CH 3 ), C 3 H 6 + ( m / z 42, loss of C 2 H 2 ), and C 3 H 4 + ( m / z 40, loss of C 2 H 4 ). Dissociative ionization paths were calculated at the CBS-QB3//B3LYP/6-311+G(d,p) level of theory, The literature mechanisms for CH 3 and C 2 H 4 losses cannot be reconciled with the experimental results and the reaction paths and energetics are revisited. Methyl radical loss is found to form the methylcyclopropenyl cation, while ethylene loss results in the allene radical cation rather than ionized propyne.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".