Distant dipolar fields among nuclear spins on macroscopic scales in the gas phase are reported for the first time. Their observation via interatomic multiple quantum coherences requires high nuclear spin polarization corresponding to spin temperatures of a few mK, which is generated in laser-polarized ${}^3\mathrm{He}$, and proper control of the gas diffusion through a heavier buffer gas. This combination of physics at low and ambient temperatures opens up new ways of studying the relative translational diffusion of atoms and of gas diffusion in structures with a large range of length scales.

• Received 5 December 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.213001