Ring strain integrity in the absorption spectrum of β-propiolactone: VUV spectroscopy in the photon energy 4.6–10.8 eV
Bibliographic record
Abstract
New absolute cross-section values are reported from high-resolution vacuum ultraviolet (VUV) photoabsorption measurements of β-propiolactone in the photon energy range 4.6–10.8 eV (268–115 nm). The assignment of the different vibronic features has been performed with the aid of quantum chemical calculations that provide vertical energies, oscillator strengths and harmonic frequencies. The joint experimental and theoretical methodology employed provides a comprehensive review of the electronic state spectroscopy of CH 2 CH 2 CO 2 . A photoelectron spectrum has also been recorded from 10 up to 24 eV and compared to earlier data in the literature. A new value of (10.560 ± 0.002) eV for the ground ionic state adiabatic ionisation energy is recommended. The vibrational features in the spectral bands are assigned to C=O stretching, v 3 ′ a ′ , CH 2 wagging, v 6 ′ a ′ , ring C–O stretching, v 10 ′ a ′ , and C=O in-plane bending, v 13 ′ a ′ modes. Potential energy curves for the lowest-lying electronic excited states, as a function of the C–O/C=O coordinates, have been obtained from time-dependent density functional theory (TD-DFT). Ring strain integrity is shown to be a fragile mechanism upon electronic excitation. The calculations have also shed light on the relevant internal conversion from the electronic excited states governing the nuclear dynamics with significant pre-dissociative character of the lowest-lying electronic states.
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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 | 0.001 |
| 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".