Recoil distance method lifetime measurements of the 2⁺₁ excited states in ⁸⁴Kr and ⁹⁴Sr
Bibliographic record
Abstract
Intense re-accelerated beams delivered by the Isotope Separator and Accelerator (ISAC-II) facility at TRIUMF, Canada’s national laboratory for particle and nuclear physics, permit access to nuclear structure information for a wide range of radionuclides via in-beam γ-ray spectroscopy with the TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer (TIGRESS), a high-efficiency and Compton-suppressed segmented high-purity germanium (HPGe) detector array. Electromagnetic transition rates measured via Doppler-shift lifetime techniques such as the recoil distance method (RDM) are recognized as a sensitive probe of collective behavior and shape deformation and can be used to discriminate between model calculations. To take advantage of this opportunity, the TIGRESS Integrated Plunger (TIP) has been constructed at Simon Fraser University (SFU). The TIP infrastructure supports Doppler-shift lifetime measurements via the RDM using a 24-element TIP CsI(Tl) wall for charged-particle identification. A commissioning experiment aimed towards a high-precision measurement of the lifetime of the 2⁺₁→ 0⁺₁ transition in ⁸⁴Kr was performed using Coulomb excitation (Coulex) coupled with an RDM lifetimem easurement of the stable ⁸⁴Kr beam. A rare isotope beam (RIB) experiment was also performed to measure the lifetime of the 2⁺₁→ 0⁺₁ transition as well as the reduced transition probability B(E2; 2⁺₁ → 0⁺₁) in ⁹⁴Sr near the shape transition region around A = 100 and N = 60. A Monte Carlo code for simulating γ-ray spectra has been coupled with a likelihood ratio χ2Λ data analysis method in order to determine the lifetime in the two presented experiments. The device, experimental approach, analysis, and results are presented and discussed.
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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 | 0.000 | 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 | 0.000 |
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".