Measurement of the dressed spin effects of $^3$He

A new experiment to search for neutron electric dipole moment (EDM) will use ultracold neutrons produced in superfluid helium. Polarized $^3$He will be utilized as a comagnetometer to detect the precession frequency of polarized ultracold neutron. An RF magnetic field will be applied to modify the effective magnetic moments of neutron and $^3$He. This dressed- spin technique, proposed by Golub and Lamoreaux, aims at a reduction of the systematic uncertainty of the EDM measurement. Using a polarized $^3$He cell prepared with the meta-stability exchange technique, we have studied the dressed spin effects for $^3$He for a variety of dressing field configurations. Results from this measurement will be presented and compared with theoretical calculations. Implications of this study on the neutron EDM experiment will also be discussed.