Hamburg 2001 – scientific programme
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TT: Tiefe Temperaturen
TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten
TT 6.74: Poster
Monday, March 26, 2001, 14:30–17:00, Rang S\ 3
Adsorption of liquid helium on Cs: a system which reveals many interesting features in non-wetting behaviour — •Jürgen Klier, Valentin Iov, and Paul Leiderer, — Fakultät für Physik, Universität Konstanz, Postfach 5560 M676, D-78457 Konstanz
Generally liquid helium is known to grow as a thick wetting film on any substrate walls. However, some experiments revealed that the alkali metals Cs and Rb are the only surfaces which are non-wetted by liquid 4He. Two different ways for preparing Cs surfaces have been used: quench-condensed Cs at low temperature and Cs grown from the liquid state at room temperature. The first method provides a rough Cs surface, in contrast with the latter which seems to result in a much smoother surface. As expected, contact angle measurements have shown different results, although the wetting temperature was the same in most cases. Different hysteresis behaviour have been observed between the advancing and receding He-film which we explain on the basis of a new model taking into account the existence of micro-puddles [1]. In addition, our latest experiments using photo-electron spectroscopy to measure very sensitively the thin-film state on a quench-condensed Cs surface show surprising results. Far from the coexistence line there is only little adsorption of helium. However, very close to coexistence there is a rapid growth of helium up to about two monolayers, but still the surface is nonwet under usual convention. These results will be discussed on the basis of 2-dimensional (2D) gas or liquid adsorption and possible phase changes in 2D.
[1] A. Wyatt and J. Klier, Phys. Rev. Lett. 85, 2769 (2000).