Light-induced atomic desorption and diffusion of Rb from porous alumina

Abstract

We present the first study of light induced atom desorption (LIAD) of an alkali atom (Rb) in porous alumina. We observe the variation due to LIAD of the rubidium density in a vapor cell as a function of illumination time, intensity and wavelength. The simple and regular structure of the alumina pores allows a description of the atomic diffusion in the porous medium in which the diffusion constant only depends on the known pore geometry and the atomic sticking time to the pore wall. A simple one-dimensional theoretical model is presented which reproduces the essential features of the observed signals. Fitting of the model to the experimental data gives access to the diffusion constant and consequently the atom-wall sticking time and its dependence on light intensity and wavelength. The non-monotonic dependence of the LIAD yield on the illumination light frequency is indicative of the existence of Rb clusters in the porous medium

Laser-driven self-assembly of shape-controlled potassium nanoparticles in porous glass

“…Their control provides a tool for driving the evolution of nanoscale systems, where the atomic mobility is strongly affected by the interaction with the substrate [4,2,5]. The atomic transport in adsorbing porous materials is governed by the adsoprtion/desorption events at the pore's surface, where atomic nanoaggregates are assembled as a consequence of atomic surface diffusion and nucleation [2,6,7,8].…”

“…Upon visible illumination, the atomic desorption probability from atomic layers covering the pore's surface increases; consequently also the atomic diffusion coefficient, which is proportional to the desorbing rate, rises. The atomic motion can be thus modelled as a random sequence of free flights between the pore walls, interrupted by adsorption events at the nanopore surface [2]. As an atom sticks to the surface, it can be either desorbed again -with a light-enhanced probability -or can be trapped at surface defects where metastable metallic nanoparticles (NPs), characterized by defined surface plasmon bands, are formed [6,7].…”

Low Energy Atomic Photodesorption from Organic Coatings

“…Evidence of LIAD was in fact found from porous glass, a chemically altered silica matrix, characterized by an interconnected network of pores of controlled diameter, usually in the range of 10-100 nm. LIAD effect from bare quartz [38] and from porous alumina with Rb atoms [26] was also demonstrated. In this context, as a consequence of the tight confinement of the desorbed atoms, light-assisted formation of metallic nanoparticles was observed in Rb, Cs and K from porous glass [22][23][24][25]28,29] and also from Vycor glass [27].…”

“…For example, the time response can be dramatically different in a sealed vessel such as a spectroscopy vapor glass cell, or in an open environment, such as a continuously evacuated vacuum chamber. We limit the discussion to models developed for organic coatings in sealed cells, although phenomenological treatments of low-energy non-resonant photodesorption have been proposed for porous materials [26] and for metal layers in the context of cold atoms experiments [56]. These models, developed originally for PDMS [6] and paraffin [20], focus their attention on the complete system formed by the vapor phase and the coating, in order to model the complex interplay among adsorption and desorption fluxes in various conditions.…”

“…Several works have been produced on the photodesorption of different atoms from organic compounds named above or porous materials [22][23][24][25][26][27][28][29] in sealed glass cells, high-vacuum chambers or photonic bandgap fibers.…”