New spectra of (HCl)3 and (HCl)4: Is the tetramer planar?
Bibliographic record
Abstract
Spectra of HCl trimer and tetramer are studied in the H-Cl fundamental stretch region using a rapid-scan optical parametric oscillator source to probe a pulsed supersonic slit jet expansion. Compared to previous work on these weakly bound clusters, the effective rotational temperature in the jet (≈2.3 K) is much lower, resulting in reduced spectral congestion. For the trimer, this enables detection and assignment of all six isotopologue components of the degenerate perpendicular band around 2809 cm-1, and these new data result in significant changes in the resonant vibrational coupling parameters used to model isotopic effects. Very weak trimer "hot" bands are also observed. For the tetramer, a weak parallel band around 2790 cm-1 is observed and analyzed. Its presence suggests that the tetramer structure is (slightly) nonplanar, as predicted by modern ab initio calculations, and the validity of this conclusion is discussed. The much stronger perpendicular band of the tetramer around 2776 cm-1 has a considerable amount of partly resolved rotational structure, but it is lifetime-broadened (≈0.01 cm-1) and too congested to permit detailed analysis. Applying an expanded resonant vibrational coupling model, with input from the parallel band results, the overall shape of the perpendicular band is simulated with reasonable accuracy for two rotational temperatures, 2.3 and 13 K.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".