(i) increasing width of the pore neck, (ii) a decrease in neck length
for very short necks (for longer necks, the transition temperature is
insensitive to the length), (iii) a stronger holding potential for the
adsorbate.
Argon adsorption in the ink-bottle-pore was also investigated at
a supercritical temperature. There are two peaks in the plot of excess
pore density versus pressure; the first peak is a consequence
of the sigmoidal shape of the pressure dependence of the bulk
gas density, and the second peak is due to the further compression
of the adsorbate and is manifested only at high temperatures.