Photodissociation of the geometric isomers of 1,2-dibromoethylene
Bibliographic record
Abstract
Resonance-enhanced multiphoton ionization (REMPI) spectra of 1,2-dibromoethylene (C(2)H(2)Br(2)) obtained using ultraviolet fundamental wavelengths between 280 and 312.5 nm and monitoring Br(+) fragments in a time-of-flight mass spectrometer are found to differ dramatically from those reported in the literature by detecting C(2)H(2)(+). Laser power plots suggest that the initial excitation process is (2+1) REMPI, which accesses parent excited states between 156.25 and 140.84 nm. Unlike the spectra obtained by monitoring C(2)H(2)(+), the spectra obtained by monitoring Br(+) appear to be identical regardless of which parent isomer (cis or trans) is excited. Based on energetics, it is proposed that Br(+) ions are formed by excitation and fragmentation of a ground-state 2-bromovinyl radical intermediate (CHBr=CH.) generated by the rapid excited-state dissociation of the parent molecules. Density-functional theory calculations using the hybrid Perdew-Burke-Ernzerhof (PBE1PBE) functional and the 6-311++G(3df,3pd) basis set confirm that the barrier to isomerization for the 2-bromovinyl radicals formed from the cis- and trans-1,2-dibromoethylenes is low, which explains why the resultant REMPI spectra cannot be distinguished based on their isomeric origin. Electronic spectra calculated for the 2-bromovinyl radical using the long-range-corrected hybrid PBE functional (LC-omegaPBE) are in qualitative agreement with experimental results.
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How this classification was reachedexpand
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) | 0.000 | 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) | 0.000 | 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 teacher head, 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".