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arXiv:1405.1159 · Journal of Experimental and Theoretical Physics

Accurate measurement of the sticking time and sticking probability of Rb atoms on a polydimethylsiloxane coating

Sergey Nikitich Atutov, Alexander Ivanovich Plekhanov

Published Jan 1, 2015• 12 citations

Abstract

We present the results of a systematic study of Knudsen’s flow of Rb atoms in cylindrical capillary cells coated with a polydimethylsiloxane (PDMS) compound. The purpose of the investigation is to determine the characterization of the coating in terms of the sticking probability and sticking time of Rb on the two types of coating of high and medium viscosities. We report the measurement of the sticking probability of a Rb atom to the coating equal to 4.3 × 10−5, which corresponds to the number of bounces 2.3 × 104 at room temperature. These parameters are the same for the two kinds of PDMS used. We find that at room temperature, the respective sticking times for high-viscosity and medium-viscosity PDMS are 22 ± 3 μs and 49 ± 6 μs. These sticking times are about million times larger than the sticking time derived from the surface Rb atom adsorption energy and temperature of the coating. A tentative explanation of this surprising result is proposed based on the bulk diffusion of the atoms that collide with the surface and penetrate inside the coating. The results can be important in many resonance cell experiments, such as the efficient magnetooptical trapping of rare elements or radioactive isotopes and in experiments on the light-induced drift effect.

DOI: 10.1134/s1063776115010094

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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°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.

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