Observation of nuclear spin waves in spin-polarized atomic hydrogen gas

We have observed narrow, distinct resonances in the NMR spectrum of dilute spin-polarized atomic hydrogen gas (nroughly-equal1016 atoms/cm3). The dependence of the observed spectra on temperature, density, polarization, and magnetic field gradient is consistent with theoretical predictions for spin-wave excitations damped by diffusion. We have measured the parameter μ, which is a measure of the importance of exchange effects in spin transport processes, and the diffusion coefficient D0, both of which are in reasonable agreement with theory