  We show that high-resolution laser spectroscopy can probe surface
interactions of gas confined in nano-cavities of porous materials. We report on
strong line broadening and unfamiliar lineshapes due to tight confinement, as
well as signal enhancement due to multiple photon scattering. This new domain
of laser spectroscopy constitute a challenge for the theory of collisions and
spectroscopic lineshapes, and open for new ways of analyzing porous materials
and processes taking place therein.
