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We have performed thermal conductivity and adsorption isotherm measurements to investigate the system formed by Xe adsorbed on resorcinol-formaldehyde (RF) aerogel. Below 80 K, the thermal conductivity of the Xe/RF-aerogel system is essentially identical to that of the bare RF aerogel; however, above this temperature the thermal conductivity of the system increases significantly above that of the bare aerogel. Adsorption isotherm measurements indicate that Xe incompletely wets the RF aerogel below Xe's bulk triple point temperature. The thickness of the Xe film that forms on the RF aerogel decreases with decreasing temperature. By 80 K the total amount of Xe present on the aerogel in equilibrium with the saturated vapor pressure is less than the amount needed to form about 1.5 atomic layers of Xe on the substrate. We attribute the observed changes in the thermal conductivity of the Xe/aerogel system to changes in the wettability of the aerogel by the Xe film.

The effects of adsorption of xenon to the thermal conductivity of a resorcinol-formaldehyde aerogel were investigated in a temperature range from 20 to 120 K. It was found that at temperatures below 75 K, the adsorbed xenon has little effect on the thermal conductivity. Rapid rises of the thermal conductivity develop at temperatures around 75-80 K with magnitudes roughly proportional to the amount of xenon adsorbed. The effect is explained as due to adsorbed xenon atoms that enhance the neck connection between aerogel particles.