Nonlinear behaviour of positive ions in normal liquid 3He : a comparison between experiment and a parameterless theoretical prediction.

We have measured positive ion velocities v in normal liquid 3He as a function of electric field E from l0^4 to 2 x 10^5 V/m for a number of temperatures T and pressures P within 3 < T < 50 mK, 1.6 < P < 29 bar. The highly nonlinear variation of U with E observed for U 5 2k,T/hk, is shown to be in excellent quantitative agreement with the theory recently developed by Fetter and Kurkijarvi and by Bowley