Capillary condensation of helium in narrow slit pores

We study the capillary condensation of liquid ⁴He films inside narrow slit pores with a density functional model and compare the result to the predictions of the Kelvin equation. Our investigation, in the wetting situation, indicates that pores with sizes up to 100 Å are still too small for the macroscopic thermodynamic arguments used to derive the Kelvin equation to be successful. The discrepancy is tentatively attributed to the use of a slab-density model and bulk parameters in the region of very thin films.