We investigate the behavior of the collective excitations of adsorbed 4He in an ordered hexagonal mesopore, examining the crossover from a thin film to a confined fluid. Here we present the inelastic scattering results as a function of filling at constant temperature. We find a monotonic transition of the maxon excitation as a function of filling. This has been interpreted as corresponding to an increasing density of the adsorbed helium, which approaches the bulk value as filling increases. The roton minimum exhibits a more complicated behavior that does not monotonically approach bulk values as filling increases. The full pore scattering resembles the bulk liquid accompanied by a layer mode. The maxon and roton scattering, taken together, at intermediate fillings does not correspond to a single bulk liquid dispersion at negative, low, or high pressure.
@article{arxiv.1805.04188,
title = {Maxon and roton measurements in nanoconfined $^4$He},
author = {Matthew S. Bryan and Paul E. Sokol},
journal= {arXiv preprint arXiv:1805.04188},
year = {2018}
}