Suppression of spin-exchange relaxation using pulsed parametric resonance.

We demonstrate that spin-exchange dephasing of Larmor precession at near-Earth-scale fields is effectively eliminated by dressing the alkali-metal atom spins in a sequence of ac-coupled 2π pulses, repeated at the Larmor precession frequency. The contribution of spin-exchange collisions to the spectroscopic linewidth is reduced by a factor of the duty cycle of the pulses. We experimentally demonstrate resonant transverse pumping in magnetic fields as high as 0.1 G, present experimental measurements of the suppressed spin-exchange relaxation, and show enhanced magnetometer response relative to a light-narrowed scalar magnetometer.