Molecular-scale density oscillations in water adjacent to a mica surface.
High-resolution specular x-ray reflectivity of the mica(001)-water interface under ambient conditions reveals oscillations in water oxygen density in the surface-normal direction, giving evidence of interfacial water ordering. The spacings between neighboring water layers in the near-surface, strongly oscillatory region are 2.5(2)-2.7(2) A, approximately the size of the water molecule. The density oscillations extend to about 10 A above the surface and do not strictly maintain a solvent-size periodicity as that in interfacial liquid metal and hard-sphere molecular liquids. We interpret this oscillatory density profile of the interfacial water as due to the "hard-wall" effect of the molecularly smooth mica surface.
Cheng
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Environmental Research Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Fenter
P
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Nagy
K L
KL
Schlegel
M L
ML
Sturchio
N C
NC