We show that indirect spin-spin interactions between effective spin-1/2 systems can be realized in two parallel one-dimensional optical lattices loaded with polar molecules and/or Rydberg atoms. The effective spin can be encoded into low-energy rotational states of polar molecules or long-lived states of Rydberg atoms, tightly trapped in a deep optical lattice. The spin-spin interactions can be mediated by Rydberg atoms, placed in a parallel shallow optical lattice, interacting with the effective spins by charge-dipole (for polar molecules) or dipole-dipole (for Rydberg atoms) interaction. Indirect
XX, Ising, and
XXZ interactions with interaction coefficients ${J}^{\ensuremath{\perp}}$ and
Jzz sign varying with interspin distance can be realized, in particular, the ${J}_{1}\ensuremath{-}{J}_{2} XXZ$ model with frustrated ferro-(antiferro-)magnetic nearest (next-nearest) neighbor interactions.
In a helium–hydrogen mixture at T = 300 K, the polarization degree of hydrogen spins, both electron and nuclear, was determined to be as high as (5 ± 1)%. The role of the main processes giving rise to the formation of spin-polarized H atoms has been discussed. It is shown that an effective transfer of angular momentum from the preliminarily optically oriented He * (2 3 S 1 ) atoms to the H atoms is not due to the direct chemi-dissociation of the H 2 molecules by the He * atoms alone, or due to Penning ionization of these molecules followed by the ion-molecular rearrangement reaction H 2 + + H 2 → H 3 + + H alone, but to their summary action. The relative importance of the two mechanisms depends on the rotational temperature and total gas pressure.