Anomalous neutron reflectivity at the quartz/H2O-D2O interface

The neutron reflectivity from the quartz/H2O-D2O interface at room temperat ure has been investigated. It has been found that it is not possible to fin d a satisfactory fit to the measured data using a simple model containing a roughness of the quartz/liquid interface. Instead, the measured data turne d out to exhibit an anomalously enhanced reflectivity for momentum transfer s Q > 0.02 Angstrom(-1). In order to quantify the anomalies observed, the e xistence of an additional (however fictitious) layer had to be assumed for the model being used for fitting the experimental data. The scattering leng th density of the fictitious layer was found to be considerably higher than that of the bulk liquid. (C) 2000 Elsevier Science B.V. All rights reserve d.