Honoured with poster prize and introductory talk

Robert Seidel's results are important for the design of experiments and for the correct interpretation of data. Credit:HZB

Mean free path of electron scattering in liquid water considerably shorter than supposed

Dr. Robert Seidel from the Institute for Methods of Material Development (EM-IMM) won the poster prize for “Water & Aqueous Solutions" at the renowned Gordon Research Conference (GRC) in Holderness, USA, in August 2016. Associated with the award was also the opportunity to present his results in a 15-minute talk at the GRC. Seidel presented his newest findings on angular distribution of photoelectrons in liquid water. He obtained these findings with the LiquidjetPES and SOL³PES liquid microjet facilities at the UE52-SGM beamline of BESSY II.

The mean free path for electron scattering in liquid water can be estimated by comparing it to the angular distribution of the photoelectrons in gas-phase water. This quantity is important for determining the sampling depth relative to the surface of the water that the signal of the electrons emanated from.

Seidel's data now show that the previous models overestimate this mean free path (MFP) by up to two orders of magnitude. The mean free path for electron energies less than 70 eV is actually very much smaller than assumed until now. At a kinetic energy of 25 eV, the MFP is only about 0.6 nanometres. “As a result, photoelectron spectroscopy experiments using low electron energies hardly penetrate into the material at all, sensing instead the surface”, explains Seidel. These new findings will likely be very useful now indeed to many other teams for designing experiments and correctly interpreting the data.