Muonium Formation as a Probe of Radiation Chemistry in Sub- and Supercritical Carbon Dioxide
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Bibliographic record
Abstract
Muonium (Mu = μ + e - ), which can be considered a light isotope of the H atom, has been observed for the first time in supercritical CO 2 (ScCO 2 ). It is unreactive on a time scale of a few microseconds and over a wide density range from well below to well above the CO 2 critical density ρ c = 0.47 g/cm 3 . The fraction of muon polarization in muonium, P Mu, does not vary significantly at low densities but changes quickly at the highest densities, approaching zero. This density dependence is reflected in a concomitant increase observed in the lost fraction of polarization, P L, demonstrating that the dynamics of Mu formation and depolarization in ScCO 2 is a direct probe of radiolysis effects in the terminal muon radiation track. In marked contrast to previous studies in hydrogen-containing solvents, C 2 H 6 and H 2 O, over comparable density ranges, the diamagnetic fraction, P D, was found to be almost independent of density in CO 2, attributed to the formation of the stable solvated MuCO 2 + molecular ion in this hydrogen-free solvent. The differing density dependences of both the Mu and the diamagnetic fraction in CO 2, in comparison with the rather similar trends seen for both in C 2 H 6 and H 2 O, supports previous claims of a significant role played by proton (muon) transfer reactions in the competing processes involved in Mu formation in hydrogen-containing solvents. In addition to this being the first report of radiolysis effects accompanying energetic positive muons stopping in ScCO 2, it is the only report of end of track effects in this solvent, which has many applications in nuclear waste management and green chemistry. With a mass intermediate between that of the electron, which has provided most radiation−chemistry studies in ScCO 2 to date, and the proton (or alpha-particle), implanted muons provide a unique data set, characteristic of higher LET radiation, that may be relevant to radiolysis effects induced in ScCO 2 by alpha decay from heavy nuclei, for which there are no comparable studies.
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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 it