Electronic spin polarization with an optical centrifuge

We investigate, both theoretically and experimentally, the mechanism behind the creation of a macroscopic magnetization in a gas of paramagnetic molecules with an optical centrifuge, reported in [Phys. Rev. Lett. 118, 243201 (2017)10.1103/PhysRevLett.118.243201]. Our analysis shows that the centrifuged super-rotors and noncentrifuged molecules are polarized in opposite directions, while the net magnetic moment of the whole ensemble at the end of the interaction with the laser pulse remains close to zero. As the super-rotors are more stable against reorienting collisions, their spin polarization, which points along the centrifuge axis, decays more slowly than the oppositely oriented polarization of the noncentrifuged molecules. The latter lose their directional rotation much more quickly and with it the polarization of their electronic spin. We show numerically that owing to this difference in decay rates, a net magnetization in the direction of the centrifuge is generated. The proposed model is supported by experimental data.