Soft x-ray spectroscopy of organic and organometallic molecules and polymers
Bibliographic record
Abstract
In this thesis, two aspects of research in soft X-ray absorption spectroscopy chemistry are explored. The first objective was to measure the natural circular dichroism of small chiral organic molecules at soft X-ray wavelengths. The second objective was to characterize the electronic structure and spectra of a series of organometallic polymers. The goal of the first part of this thesis was to enhance the sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to the intrinsic “handedness” of chiral organic molecules. The phenomenon of X-ray natural circular dichroism (XNCD) has been well described by theoreticians; however, there have been few successful measurements reported, mainly due to the weakness of the effect and the difficulty of preparing suitable samples. The fourth chapter of this thesis outlines the requirements for XNCD experiments and the efforts made to prepare appropriate samples. The goal of the second part was to use NEXAFS spectroscopy as an analytical technique for the elemental and chemical characterization of innovative materials based on organoiron compounds. The interpretation of transition metal compounds by NEXAFS spectroscopy is difficult due to complex interactions between the metal and its surroundings. Two approaches are commonly used; an atomic multiplet model and a covalent bonding model, which lead to conflicting spectral assignments. Earlier NEXAFS studies of metallocene complexes were found to be lacking as these two models were not adequately rationalized. Owing in part to greatly improved instrumental sensitivity and to efficient theoretical calculations, the interpretation of NEXAFS spectra for a series of metallocene and metal arene complexes was refined. Enhanced understanding of the spectroscopy of these compounds eventually contributed to the characterization of a series of organometallic polymeric materials.Underlining these studies is the remarkable complementarity of NEXAFS spectroscopy and chemistry. A comprehensive understanding of the chemistry of the samples examined in the measurement of XNCD is shown to be crucial for a successful advancement of this spectroscopy. In return, optimization of soft X-ray spectroscopy of metallocenes is demonstrated to remarkably benefit the understanding of the organometallic polymers.
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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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".