EFFECT OF DIPOLAR FIELDS IN HIGHLY MAGNETIZED SAMPLES OF LIQUID HE-3-HE-4 MIXTURES

NMR free induction decay signals obtained in highly polarized liquid H e-3-He-4 mixtures in a U-shaped cell and in a coil-shaped cell signifi cantly differ from the signal one would Obtain from independently prec essing spins. We have analysed the spin dynamics using two different m odels. Both consider the precession of the local magnetization in the dipolar field produced by the remainder of the sample. The first model explains the observed phenomena qualitatively; the second, solved num erically, reproduces satisfactorily the structure of experimental spec tra.