Electron stimulated desorption of H<sup>−</sup>from thin films of 5-halouracils
Bibliographic record
Abstract
We present measurements of low-energy (1–20 eV) electron stimulated desorption (ESD) of H− from thin films of 5-halouracils (5-XU, X = F, Cl, Br and I) condensed on polycrystalline Pt. The onset for H− desorption is ∼5.0 eV. For all 5-XU a single dissociative electron attachment (DEA) H− peak is observed, which is attributed to at least two dissociation channels at approximately 7.1 and 8.6 eV, resulting from N–H and C–H bond cleavage, respectively. Their relative contribution is parent-molecule dependent. Also, for a given molecule, these dissociation channels are affected differently by the metal, and the DEA maximum shifts by ∼0.5 eV as the film thickness increases. Above 10 eV, dipolar dissociation (DD) is the dominant H− formation mechanism. The yields of H− vary in the following relative order (T = thymine, U = uracil): T > U > 5-FU > 5-ClU > 5-BrU > 5-IU. A model is developed to explain the film thickness dependence of the desorbed anion signal: above a coverage of ∼1 monolayer (ML), the film thickness dependence of the H− ESD yield is interpreted in terms of incident electron and desorbing ion transmission within the films. The main difference in the thickness dependence of H− produced via DEA and DD is attributed to the fact that electron transfer to the metal from the transient molecular anion leads to dramatic decrease in the H− ESD signal below ∼1 ML, whereas it does not affect significantly DD, since its intermediate state is neutral.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| 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".