J. Phys. II France
Volume 3, Numéro 6, June 1993
Page(s) 761 - 766
DOI: 10.1051/jp2:1993165
J. Phys. II France 3 (1993) 761-766

Surface diffraction studies of 2D crystals of short fatty alcohols at the air-water interface

A. Renault1, J.F. Legrand2, M. Goldmann3 and B. Berge1

1  Laboratoire de Spectrométrie Physique, URA08, Université J. Fourier, B.P. 87, 38402 Saint Martin d'Hères, France
2  European Synchrotron Radiation Facilities, B.P. 220, 38043 Grenoble, France
3  PSI, Institut Curie, 11 rue P. et M. Curie, 75005 Paris, France

(Received 9 April 1993, accepted 27 April 1993)

Using X ray surface diffraction we have investigated crystalline monolayers of short alcohols (1-decanol to 1-tetradecanol) at the air-water interface in the vicinity of the first order transition corresponding to 2D melting ( $T_{\rm m}$(2D)). The diffraction patterns in the solid phase are in agreement with a 2D hexagonal close-packing. The lattice parameter value is 5.00 Å just below $T_{\rm m}$(2D) and amounts 4.90 Å at $T_{\rm m}(2\rm D)-20$ K. The resolution limited Bragg peaks indicate a large crystalline coherence length. At the approach of the 2D melting point, the observed increase of the Debye Waller factor is attributed to critical fluctuations.

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