Vibrational dependence of the torsional tunneling splitting and the <i>a</i> to <i>b</i> intensity evolution in the OH overtone spectra of CH<sub>3</sub>OH
Bibliographic record
Abstract
An ab initio investigation of the OH-stretching overtone of methanol is presented aimed at interpretation of two of the interesting features reported in recent supersonic-jet infrared-laser-assisted photofragment spectroscopy (IRLAPS) studies, namely, (i) a monotonic decrease of the torsional E A splitting as υOH increases, (ii) an evolution of the a-type transition moment towards dominance at higher excitations of the OH-stretching vibration. At the MP2 level with a 6-311+G(3df,2p) basis set, one-dimensional functions for the potential energy, dipole moment (a and b directions), barrier height V3, and torsional constant F have been mapped out as a function of the OH-bond length with the remaining structure relaxed. All ab initio quantities have been expressed as Taylor-series expansions in the dimensionless OH normal coordinate, q. Calculations have been carried out in the harmonic basis set to yield vibrational energies and eigenfunctions. The latter have been used to evaluate the torsional parameters (V3, F) and the resulting E A torsional splittings at each OH excitation, and to compute the evolution of the infrared transition intensity ratio [Formula: see text]a/b. The ab initio results reproduce the reported decrease in E A splitting by a factor of 5 in going from υOH = 0 to υOH = 6, with a maximum deviation of 19% at the highest excitation. The calculated variation in [Formula: see text]a/b is in qualitative agreement with the experimental trend, showing the observed sharp rise at high υOH. PACS Nos.: 33.20E, 33.80B
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How this classification was reachedexpand
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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) | 0.001 | 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
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