Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 28: Adsorption an Oberfl
ächen III

O 28.7: Vortrag

Donnerstag, 27. März 2003, 12:45–13:00, FOE/ANOR

Local Structures at Liquid Surfaces — •G. Andersson and H. Morgner — Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnestr.3, 04103 Leipzig

We established Neutral Impact Collision Ion Scattering Spectroscopy (NICISS) as method for the investigation of concentration depth profiles at liquid surfaces with a depth resolution of some  Å[1]. The inelastic loss of energy of the projectiles by low angle scattering and electronic excitations is used to determine the depth of the target atoms.

Varying the angle of incidence of the projectiles we are now able to reveal also local structures of molecules within a surface. The 3-dimensional distribution of matter around a target atom causes an inelastic loss of energy of the projectiles, which depends on the angle of incidence of the projectile. Since molecules in a liquid surface do not have a preferred orientation with respect to the azimuth we are able to probe the distribution of matter by only varying the angle of incidence of the projectiles. Evaluating the inelastic loss of energy as a function of the angle of incidence the amount of matter distributed around the target atom can be determined. At surfaces of solutions we are able to probe the local structure of the different components. In the case of the ionic surfactants tetrabutyloniumsalts solved in formamide we found, that the anions and cations are located differently in the surface. The cations as the bigger species have a flat local environment while the anions layer are found in a local deepening with a depth of some  Å. At surfaces of pure liquids the orientation of molecules can be determined.

[1] G. Andersson, and H. Morgner, Surf. Sci. 445 (2000) 89