Radioisotope

β⁻ max (MeV)

γ energy (KeV)

Half-life

Stable daughter

¹⁴⁹Pm

1.071

285.9 (3%)

2.21 d

¹⁴⁹Sm

¹⁶¹Tb

0.593

74.60 (5.8%)

6.88 d

¹⁶¹Dy

¹⁶⁶Ho

1.855

80.57 (6.2%)

1.11 d

¹⁶⁶Er

¹⁷⁷Lu

0.492

208.36 (11%)

6.73 d

¹⁷⁷Hf