Measurement of transverse spin-relaxation rates in a rubidium vapor by use of spin-noise spectroscopy

Spin noise sets fundamental limits to the attainable precision of measurements using spin-polarized atomic vapors and therefore merits a careful study. On the other hand, it has been recently shown that spin noise contains useful physical information about the atomic system, otherwise accessible via magnetic-resonance-type experiments. We here show in yet another manifestation of the fluctuation-dissipation theorem, that spin noise reveals information on the spin-coherence dissipation properties of the atomic system, described by 1∕T₂, the transverse spin-relaxation rate. We present the high-resolution measurements of spin noise at a low magnetic field, leading to an accurate comparison of the extracted relaxation rates with the ones inferred from traditional magnetic-resonance-type measurements in optical pumping experiments.