Beta decay of12B and12N to the first excited state of12C (4.44 MeV)

The branching ratios of the beta-decay of¹²B and¹²N to the 4.44 MeV state in¹²C were determined by (βγ-coincidences to be (1.182±0.019)% and (1.898±0.032)% of the total rate, resp. This givesft ^?=(1.407±0.023) · 10⁵ s andft ⁺=(1.406±0.024) · 10⁵ s. For theft-asymmetryδ=(ft ⁺/ft ^?)?1 the valueδ=?(1±14) · 10^?3 was obtained. This is in contrast to other GT mirror transitions which show positiveδ of a few percent.