Measurement of the size of micrometric voids in dielectric media

摘要

We have developed a method to measure the characteristic interstice size of transparent porous dielectric media. The method is based upon the observation of the transient decay of alkali atoms contained in the medium pores and excited to a sufficiently long-lived state. We present a simple model describing the dependence of the decay transients on the distance L traveled by the atoms between interstice walls. Fitting of the observed transient data to the model predictions allows the determination of L. The method is tested with two well-characterized micrometric thin cells and used to measure the characteristic interstice size of several porous glass samples.