First Mobility Measurement of Ions Trapped Below the Normal and Superfluid 3He Surface

We report the first mobility measurement of ions trapped below the free surface of normal and superfluid 3 He-B. A Corbino electrode arrangement is used to measure the mobility of ions. Applying an electrostatic step potential to the Corbino electrode, a charge distribution of ions becomes inhomogeneous, which induces the motion of ions. We observe the time development of the redistribution of ions by employing a capacitive coupling method. The mobility of ions is deduced from the transient response of ions, using a distributed-constant equivalent circuit analysis. The measured mobility of both types of ions are in agreement with that in the bulk normal and superfluid 3 He.