Evaluation of the \(⁸⁹ᵐ\)Y Half-life Data

Precise determination of the \(⁸⁹ᵐ\)Y isomeric half-life is critical for nuclear structure models and activation analysis. However, historical measurements exhibit a long-standing, unresolved scatter. With the present work, we aim to resolve this statistical tension by introducing a high-resolution low-background half-life measurement and evaluating historical dataset. The \(⁸⁹ᵐ\)Y half-life was measured by using the high-energy resolution HPGe detectors of RoSphere. Statistical analysis was performed on the \(909γ (t)\) data, obtained in 11 independent measurements. This dataset is highly consistent, displaying a near-ideal reduced chi-squared (\(χ ^2\)/n.d.f.) of 0.91. Conversely, the statistical analysis, performed on the historical data, reveals some extreme statistical discrepancies. Grouping the measurements by detection methodology confirms a systematic 188 ms bias between the NaI(Tl) and HPGe data. The new measurement and statistical analysis performed in the present study do not disagree with the most precise measurement of 15.663 (5) s for the \(⁸⁹ᵐ\)Y half-life previously measured in 1995. Half-life of 15.61 (4) s was evaluated by applying the Rajeval technique on all available HPGe data. Abstract Published by the Jagiellonian University 2026 authors