Quantitative measurements of light-induced desorption of rubidium atoms from quartz substrates

We investigated the light-induced desorption (LID) of Rb atoms from quartz substrates to understand better the LID observed in alkali-metal vapor cells used in laser cooling experiments. The substrate was first exposed to Rb under ultrahigh vacuum conditions. The Rb was found to diffuse into the substrate by x-ray photoelectron spectroscopy. Rb atoms were then deposited with a density of ~10¹⁵ atoms/cm² on the surface, from which LID was observed upon irradiation by ultraviolet light. The LID rate depended linearly on the light intensity in the investigated range up to 15 mW/cm². A typical value was 10¹⁰ atoms/(s cm²) per mW/cm² at a photon energy of 4.3 eV (290 nm in wavelength). We found that the LID rate increased with photon energy in the range 1.8--4.3 eV (700--290 nm in wavelength).