Laser-ionisatiespectroscopie van 254No en 229Th in hypersonische gasjets
Bibliographic record
Abstract
Short half-lives, low production rates and the need to produce them by fusion-evaporation reactions all complicate laser spectroscopy studies of (trans)actinides. The In-Gas Laser Ionization and Spectroscopy (IGLIS) technique has been succesfully employed in studies on short-lived actinides (see for instance [1,2]). The addition of a convergent-divergent (de Laval) nozzle to create a cold hypersonic gas jet combines efficiency with sub-GHz spectral resolution. The new generation of nozzles with a Mach number of 8 enables laser spectroscopy studies of actinides with spectral resolutions around 200 MHz [3]. In this thesis several developments with regards to the IGLIS technique are investigated. One of these is a new set of de Laval nozzles designed and characterized to operate under low-stagnation-pressure conditions required for recoil sources as well as for spectroscopy studies of (trans)actinides in the JetRIS experiment at GSI [5]. This allowed for the first sub-GHz measurement of No-254. The light actinide Th-229 and its nuclear clock isomer have also attracted significant attention in the last years. A remarkable feature is the suggested short half-life ( < 10 ms) of the isomer in its, not-yet observed, singly charged state [4]. This is isotope is of interest for the development of a Th-229 based nuclear clock [6]. Preparatory studies have allowed for an accurate extraction of the ionization potentials of both Th I and Th II. Several auto-ionizing states above the second ionization potential were discovered which will be used to improve laser ionization efficiency for in-gas-jet laser spectroscopy studies of the 229Th+ isomer. [1] C. Granados et al. Phys. Rev. C, 96:054331, 2017. [2] S. Raeder et al. Phys. Rev. Lett., 120:232503, 2018. [3] R. Ferrer et al. Physical Review Research, 3:043041, 2021. [4] L. von der Wense et al. Nature, 533:47-51, 2016. [5] S. Raeder et al. Nucl. Instrum. Methods Phys. Res. B, 463:272-276, 2020. [6] S. Kraemer et al. Nature, 617:706-710, 2023.
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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) | 0.003 | 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 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".