Fourier transform infrared matrix‐isolation analysis of acetaldehyde fragmentation products after charge exchange with Ar<sup>•+</sup> under varied ionization density conditions
Bibliographic record
Abstract
The products of the Ar(•+) charge exchange ionization of acetaldehyde have been isolated and compared with related photoionization results and computational work. Acetaldehyde has been used to assess the effect of varied ion density in the ionization region of the electron bombardment matrix isolation apparatus. The amount of acetaldehyde destruction has been measured for constant gas-sample composition and constant ionization current for two anode geometries: a pin anode and a plate anode. For the same ionization current, a pin-shaped anode demonstrates higher precursor molecule destruction efficiency (85%) than the plate-shaped anode (30%), resulting in substantial effect on the yield and quantity of isolated products. When the plate anode is used, the observed infrared products correspond to matrix-isolated carbon monoxide (CO), methane (CH(4)), ketene (CH(2)CO), ethynyloxy radical (HCCO), formyl radical (HCO(•)), acetyl radical (CH(3)CO(•)), vinyl alcohol (H(2)C = CH-OH), and cationic proton-bound dimer, Ar(2)H(+). When the pin anode is used, the same products are observed with different relative proportions and new absorption features corresponding to dicarbon monoxide (CCO) and methyl radical (CH(3)(•)) are observed. The surprising observation of infrared absorptions corresponding to vinyl alcohol along with low yield of products anticipated through the analysis of photoelectron-photoionization coincidence measurements suggests that the initially formed fragmentation products are able to further react within the matrix-isolation environment to influence observed product yields. Related experiments, using the isotopomer CD(3)CHO, suggest that the observed products are formed via radical-radical reactions that occur under the high pressure conditions of the matrix isolation environment.
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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) | 0.002 | 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".