Two-photon evanescent-volume wave monitoring of desorbing Cs atoms

The two-photon fluorescence spectroscopy in the vicinity of the surface has been performed for Cesium atoms. One of the laser beams was directed perpendicularly to the surface, whereas the second one excited an evanescent wave propagating along the surface. To demonstrate its potential, this technique has been applied for a qualitative comparative study of Cs atom desorption from a glass surface versus the same surface coated with a PDMS film. That way the fluorescence line originating primarily from desorbing atoms could be spectrally isolated. The desorption flux from polymer coated surfaces is found to be significantly smaller as compared to the flux from a plain glass surface