Field Dependence of the Superfluid 3He A 1 and A 2 Transitions

We present new results on the magnetic field dependence of the superfluid transition temperatures of the A₁and A₂phases of³He. The transition temperature has been measured up to 15 T, the up to 12 T, at the melting pressure. The temperature was measured by an in situ field independent glass thermometer. The results are in agreement with extrapolations from earlier experiments, and with calculations of the splitting versus magnetic field. We were also able to obtain an estimate of the quadratic terms of the splitting, and of each of the transition temperatures. The measured quadratic terms are smaller than calculated, the negative coefficient for the quadratic term being quite unexpected.