Probing Excited Electronic States Using Vibrationally Mediated Photolysis: Application to Hydrogen Iodide
Bibliographic record
Abstract
We measure branching ratios and anisotropy parameters for the photolysis of HI( v =2, J =0) → H + I( 2 P° 1/2 )/I( 2 P° 3/2 ) over the wavelength range 297−350 nm. HI is prepared in the v = 2, J = 0 rovibrational level using direct IR absorption, and the H-atom photofragments are probed with resonance enhanced multiphoton ionization coupled with core-extraction time-of-flight mass spectrometry. The new branching ratio measurements disagree with predictions obtained from ab initio calculations and from the results of an empirical analysis based on experimental values of the HI/DI( v =0) absorption cross sections and branching ratios. Thus, we combine our new data with all existing absorption coefficient and branching fraction data for HI/DI in a global analysis that provides a new empirical determination of the final-state potential curves and transition moment functions for the four excited electronic states contributing to the A-band UV absorption continuum of HI. This analysis yields two models for the radial dependence of the excited state potential energy curves and transition dipole moment functions. The existing data cannot differentiate these models, but this work identifies a range of experiments that would do so. More generally, we demonstrate that photodissociation of vibrationally excited molecules is a sensitive probe of the repulsive excited electronic states encountered in bound-free transitions.
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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) | 0.000 | 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) | 0.000 | 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".