Spin-exchange-relaxation-free magnetometry with Cs vapor

We describe a Cs atomic magnetometer operating in the spin-exchange-relaxation-free (SERF) regime. With a vapor cell temperature of 103 degrees C we achieve intrinsic magnetic resonance widths Delta B= 17 mu G corresponding to an electron spin-relaxation rate of 300 s(-1) when the spin-exchange rate is Gamma(SE)= 14 000 s(-1). We also observe an interesting narrowing effect due to diffusion. Signal-to-noise measurements yield a sensitivity of about 400 pG/root Hz. Based on photon shot noise, we project a sensitivity of 40 pG/root Hz. A theoretical optimization of the magnetometer indicates sensitivities on the order of 2 pG/root Hz should be achievable in a 1 cm(3) volume. Because Cs has a higher saturated vapor pressure than other alkali metals, SERF magnetometers using Cs atoms are particularly attractive in applications requiring lower temperatures.