Collision of atoms with porous polymer surface: evidence of influence of bulk diffusion on anomalously long dwell time of Rb atoms

Study of Rb-vapor coated cells — Atomic diffusion and cell curing process

“…According to the Stokes -Einstein equation, which describes diffusivity to be inverse proportional to viscosity, one can speculate that on the surface of a completely polymerized PDMS with viscosity enhanced one million times, the dwell time should be one million times smaller: 10 -4 /10 6 = 10 -10 s. This is true if the polymerization does not change the attractive potential barrier on the cured PDMS film surface. Note that this estimated dwell time value is close to the one derived from the measured potential barrier on the film surface and the film temperature [19].…”

“…We estimate how deep atoms can diffuse inside a fresh polymer film l during a dwell time d. For instance, in the case of rubidium and PDMS, we have Dp =1.1•10 -3 cm 2 /sec (that is found by extrapolation the curve in Fig.2 to zero time), d =10 -4 sec from [19] and by using the…”

“…For instance, in the case of rubidium and PDMS, we have Dp =1.1•10 -3 cm 2 /sec (that is found by extrapolation the curve in Fig. 2 to zero time), d =10 -4 sec from [19] and by using the…”