Time-Resolved Measurements of the Adsorption/Desorption of Rb Atoms on Octadecyltrichlorosilane Coated Surfaces

We carry out the first time-resolved measurement of Rb atoms desorbing from octadecyltrichlorosilane coated surfaces by polarizing the atoms near the surface using an evanescent wave pump pulse and watching the subsequent intensity change of another evanescent wave probe beam, and find the mean adsorption (dwell) time to be about 400 ns at a cell body temperature of 112 degrees C. The adsorption energy is found to be 0.19 eV from the surface temperature dependence of the adsorption time. This method can be extended to study the adsorption/desorption process of other alkali atoms on other surfaces of transparent substrates with an ultimate time resolution limited by the flight time of atoms in the evanescent wave which is of the order of nanoseconds.