Equilibrium Properties of Submonolayer He^4 Films
<p>Isosteres have been measured for submonolayer films of helium-four adsorbed on a sintered copper sponge precoated with each of the other noble gases, These measurements were carried out at temperatures between 3°K and 4°K, and at coverages between 0.5 and 1.0 monolayer; the pressures e...
| Summary: | <p>Isosteres have been measured for submonolayer
films of helium-four adsorbed on a sintered copper
sponge precoated with each of the other noble gases,
These measurements were carried out at temperatures
between 3°K and 4°K, and at coverages between 0.5
and 1.0 monolayer; the pressures encountered were
in the range from 10<sup>-7</sup> Torr to 10<sup>-1</sup> Torr. On the
neon-coated substrate, the lower binding energy
and higher lateral mobility made it feasible to take
useful data at coverages as low as 0.025 monolayer.
From the isosteres, information is derived about
the partial molar entropy, entropy and heat capacity
of the film.</p>
<p>It appears that the submonolayer film is a
well-defined entity whose qualitative properties
remain unchanged as the substrate precoating is
varied, These include a transition into a highly
ordered state as the coverage is increased, a total
heat capacity which is not monotonic with coverage,
and significant lateral mobility. The transition
into the ordered state is initiated at higher coverage
as the temperature is lowered, and this anomaly is
discussed in terms of a model in which two dimensional
crystalline patches are broken up by thermal fluctuations.</p> |
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