Speaker
Description
Transport of energetic electrons through gases and dense media is invariably determined by electron scattering. In photoemission experiments, the influence of scattering can be avoided in gas-phase experiments by choosing a sufficiently dilute target, but inelastic scattering becomes noticeable as soon as atomic or molecular clusters are considered. In solids and liquids, inelastic scattering is known to produce pronounced, broad backgrounds in the kinetic energy distribution, which hardly have been explored in detail for the latter. Here, we present experimental data on the photoemission of electrons with low kinetic energy (< 30 eV) from liquid water, probed from a liquid microjet in vacuum. Data for the valence band ranging down to the ionization threshold will be shown. Results will be compared to spectra of <N> = 135 water clusters.
We show that cluster valence-band features can well be observed at kinetic energies as low as one eV, while in liquid water both valence and core-level features are blended into a structureless continuum of inelastically scattered electrons as soon as kinetic energies decrease below a limit of approximately 10 eV. This is attributed to an interplay of the change in inelastic mean free path with various scattering channels, where below this threshold it is known from gas-phase studies that electron impact ionization channels are closing.[1] A comparison with Cl 2p-core level photoemission spectra of the exemplary aqueous solute NaCl near the Cl 2p ionization threshold shows that this finding is universal for low kinetic energy electrons produced in an aqueous environment.
[1] S. Malerz, F. Trinter, U. Hergenhahn, A. Ghrist, H. Ali, C. Nicolas, C.-M. Saak, C. Richter, S. Hartweg, L. Nahon, C. Lee, C. Goy, D.M. Neumark, G. Meijer, I. Wilkinson, B. Winter, and S. Thürmer.
Phys. Chem. Chem. Phys., 2021, 23, 8246-8260 .
| Abstract Number (department-wise) | MP 18 |
|---|---|
| Department | MP (Meijer) |
