Measurement of the 7s-8s M1 transition in laser-trapped francium
Bibliographic record
Abstract
Studying fundamental symmetries at low and intermediate energies helps garner a more complete understanding of the Standard Model. In particular, atomic parity-violation tests the Standard Model at some of the lowest energies. Past results in cesium have provided the most accurate results for atomic parity-violation to date. Present results in ytterbium are reaching the accuracy levels of cesium, but have difficulties reconciling with theory due to complex atomic structures. This is why a proposed atomic parity-violation experiment in francium at TRIUMF could be advantageous. Parity-violating effects scales as ~ Z^2N, which favours francium (Z=87). Additionally, the hydrogen-like electronic configuration lends itself nicely to theoretical calculations. Furthermore, using the 7s-8s transition in francium to probe parity-violating effects is preferred due to heavily suppressed optical transitions, the caveat being the parity-violating transition is still smaller. The solution is to pair the parity-violating transition with a tunable Stark-induced transition in an interference experiment. However, coexisting with the parity-violating and Stark-induced transition is a small magnetic dipole transition. The 7s-8s transition is typically magnetic dipole forbidden, as it violates certain atomic selection rules. Nevertheless, due to the hyperfine interaction and relativistic effects there is a small mixing of states that allows for a magnetic dipole transition. Understanding this effect in francium is key for an atomic parity-violation experiment and for testing atomic theory. To date, cesium is the only alkali in which the magnetic dipole transition has been studied. The cesium results for the relativistic contribution to the magnetic dipole transition differs from theory by 15%. Hence, on our way to measure parity-violation we want to also investigate the magnetic dipole transition in francium. To do this we need to implement some key components to the existing apparatus to enable us to resolve such a small transition. Within this thesis, we will discuss the key existing and newly added features to the experimental apparatus that enabled us to observe for the first time the 7s-8s magnetic dipole transition and measure the relativistic contribution.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".