Dipolar and scalar ³He-¹²⁹Xe frequency shifts in stemless cells

We study nuclear spin frequency shifts in a $^{3}$He-$^{129}$Xe comagnetometer caused by spin polarization of $^{3}$He. We use stemless cylindrical cells to systematically vary the cell geometry and separately measure the cell shape-dependent and shape-independent frequency shifts. We find that a certain aspect ratio for a cylindrical cell cancels the dipolar effects of $^3$He magnetization in the regime of fast spin diffusion. Using this control we observe a scalar $^{3}$He-$^{129}$Xe collisional frequency shift characterized by an enhancement factor $\kappa_{\text{HeXe}} = -0.011\pm0.001$ in excellent agreement with theoretical calculation.