Sensitivity and Resolution Enhancement of Half-integer Quadrupolar Nuclei in Solid-state NMR
Bibliographic record
Abstract
Solid-state NMR studies of non-integer spin quadrupolar nuclei generally focus on the “central transition”, mI = 1/2 mI = − 1/2, since it is not perturbed by the quadrupolar interaction to first order. For samples spinning at the magic angle, analysis of the central transition line shape provides the nuclear quadrupolar coupling constant and the asymmetry parameter. For stationary samples, analysis of the central transition also provides information about the magnetic shielding tensor and its orientation relative to the electric field gradient tensor. Because of the importance of the central transition in solid-state NMR studies of half-integer quadrupolar nuclei, considerable effort has been devoted to developing techniques to enhance the signal-to-noise ratio of the central transition. To date, the most successful techniques for sensitivity enhancement of the central transition (CT) involve altering the Boltzmann equilibrium populations. Various techniques for altering these populations and the resulting CT enhancements are outlined in this contribution. Keywords: solid-state NMR; quadrupolar nuclei; sensitivity enhancement; double-frequency sweeps; FAM; RAPT; hyperbolic secant pulses
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".