Method for Measuring the Dwell Time of Spin-Polarized Rb Atoms on Coated Pyrex Glass Surfaces Using Light Shift

摘要

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 500 μm. 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 T_s. For a Pyrex glass cell coated with octadecyltrichlorosilane we find that t_s = 0.53 ± 0.03 μs at a cell wall temperature of 103 ℃. The temperature dependence of t_s is fitted to t_s = T_0 exp(E_a/kT), yielding a preexponential factor T_0 = 2.2_(-1.4)~+(5.1) ns and an activation energy E_a = 0.19 ± 0.03 eV.