Fig. 1: Adsorption and structure inside nanopores.
a Dark gray circles illustrate the adsorption behavior of 4He at 4.2 K into MCM-41 pre-plated with a monolayer of Ar gas as the pressure is increased. Here P0 is the bulk equilibrium vapor pressure of 4He. The colored stars indicate the fillings where completion of 4He layers occurs with the call-out inset images showing quantum Monte Carlo configurations of a cross-section of MCM-41 with an equilibrated Ar layer (light gray spheres) at P/P0 = 0, and the developing layers of 4He (1 layer to 3 layers plus central core) as the pressure is increased. Here the Ar is represented as a cylindrical shell for clarity. The light purple diamond indicates the filling at which experimental inelastic neutron scattering measurements were performed at Qin = 4.0 Å−1 corresponding to completely filled pores. b Quantum Monte Carlo results with binned stochastic errorbars for the radial number density of atoms ρrad(r) inside nanopores at T = 1.6 K where the scattering experiments were performed. Colors correspond to the starred filling fractions in a. As the pressure is increased, the 4He atoms form a series of concentric layers, with the density of the outer layers also increasing.
