Method for measuring the Dwell time of spin-polarized Rb atoms on coated Pyrex glass surfaces using light shift

We present a simple method for directly measuring the average dwell time of spin-polarized Rb atoms on coated Pyrex glass surfaces. The method relies on the light shift of the Zeeman resonances of spin-polarized Rb atoms pumped and probed by evanescent waves, and does not depend on the microscopic details of surface interactions. We use a cell whose length is adjustable between 70 and 500μm. The inverse of the difference between the frequency shifts caused by σ+ and σ- pump beams depends linearly on the cell length, from which we obtain the average dwell time τs. For a Pyrex glass cell coated with octadecyltrichlorosilane we find that τs=0.53±0.03μs at a cell wall temperature of 103°C. The temperature dependence of τs is fitted to τs=τ̄0exp(Ea/kT), yielding a preexponential factor τ̄0=2.2-1.4+5.1ns and an activation energy Ea=0.19±0.03eV.