Beaglehole Picometer Light Ellipsometer
A Beaglehole Picometer Light ellipsometer is optimised for interfacial characterisation at the air/liquid and air/solid interfaces. The interfacial excess can be determined to a precision and sensitivity of < 5% of a surfactant monolayer, and with complementary information or optical modelling the data can be used to quantify the adsorbed amount of material at an interface. Data can be acquired at a rate of up to 200 Hz, hence the instrument provides access to the study of fast adsorption kinetics.
The ellipsometer offers two principal benefits to users. First, it can be used as a pre-screening tool to characterise the kinetics and homogeneity of samples before neutron reflectometry (NR) beam time on FIGARO. Also, the interfacial excess of surface-active material may be compared precisely with respect to a changing variable such as solution composition or temperature. Second, the technique has greater sensitivity to species with a similar scattering length density to that of air (e.g. hydrogenated polymers). Therefore the acquisition of an “optical contrast” during NR measurements can reduce the need for as many NR isotopic contrasts thus saving beam time and deuterated chemicals. Kinetic information may be quantified to complement further the neutron reflectometry data, and inhomogeneity in free liquid surfaces can be identified prior to the modelling of NR data.