  We report molecular simulation and experimental results for simple fluids
adsorbed in activated carbon fibers (ACF), where the adsorbed phase consists of
either one or two molecular layers. Our molecular simulations involve smooth
pore-walls for large system sizes and a systematic system size-scaling
analysis. We provide calculations of the Ginzburg parameter to monitor the
self-consistency of our finite size simulation results, based on which we
establish that for system sizes smaller than 60 molecular diameters,
fluctuations are too large to uphold the finite size simulation results. We
present scaling analysis and free energy results for a system size of 180
molecular diameters. Our scaling analysis reveals a two-stage melting in our
bilayer system consistent with KTHNY scaling for the order parameter
correlation functions. Based on the Lee-Kosterlitz scaling of the free energy
surface, we establish that the transitions are first order in the thermodynamic
limit. Similar results for a monolayer established that the transitions were
continuous. We provide scaling arguments to suggest that the change in the
order of the transitions in going from a monolayer to bilayer adsorbed system
results from the interactions of defects in the multilayers. We also report
experimental measurements of CCl4 and aniline (with two confined molecular
layers) adsorbed in ACF.
