# Paulsen et al. (2024) — High precision measurement of 99Tc β spectrum

## Citation

Paulsen, M., Ranitzsch, P.C.-O., Loidl, M., et al. (2024). High precision measurement of the ⁹⁹Tc β spectrum. *Physical Review C*, 110, 055503. DOI: 10.1103/PhysRevC.110.055503

## Key Results

| Parameter | Value | Method |
|---|---|---|
| Q_β | 295.82(16) keV | MMC measurement |
| g_A^eff | 1.526(92) | Spectrum shape (CVC-fixed sNME) |
| g_V^eff | 0.376(5) | Half-life normalization |
| g_A^eff (quenched) | 0.574(36) | Half-life normalization |
| E_β | 98.51(23) keV | Theoretical spectrum integration |
| log f | −0.47660(22) | Theoretical spectrum |
| log f t | 12.3478(23) | Partial half-life |

## Methodology

- **Detector**: Metallic Magnetic Calorimeters (MMCs) at LNHB and PTB
- **Energy threshold**: 0.65 keV (orders of magnitude lower than previous measurements)
- **Energy resolution**: 0.1 keV at 383 keV
- **Nuclear model**: NUSHELLX with GLEKPN valence space, Mach interaction
- **sNME treatment**: CVC-fixed (not ESSM)

## Key Figures

- **Figure 9**: g_A-dependent theoretical β spectrum — shows dramatic shape changes for g_A ∈ {0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 2.0}
- **Figure 10**: Best-fit theoretical spectrum vs. measurement

## Limitations

- Used CVC-fixed sNME (not ESSM) → enhanced g_A value
- Song et al. (2025) contradicts this result using ESSM

## References

- [[Shape Factor C(W, g_A)]]
- [[SSM — Spectrum Shape Method]]
- [[Song et al. (2025)]]
- [[Ramalho & Suhonen (2024)]]