Time-resolved photoelectron spectroscopy was used to study the energetics and dynamics of solvated electrons in aqueous solution. Solvated electrons are generated by ultrafast photodetachment in a 100 mM aqueous NaI solution. Initially, an ensemble of strongly bound ("cold") solvated electrons and an ensemble of weakly bound ("hot") electrons in an unequilibrated solvent environment are observed. We report an ultrafast recombination channel for the "hot" electrons with a rate of (800 fs)(-1) which is in competition with thermalization occurring with a rate of (1.1 ps)(-1). The thermalized electrons recombine with the iodide radical with a rate of (22 ps)(-1). About 35% of the thermalized electrons escape geminate recombination and form free, solvated electrons. The vertical detachment energy for the solvated electron is determined to be 3.40 eV. No indication for a surface-bound electron at lower binding energies was observed.

Time-resolved photoelectron spectroscopy is performed on thymine and thymidine in aqueous solution to study the excited-state relaxation dynamics of these molecules. We find two contributions with sub-ps lifetimes in line with recent excited-state QM/MM molecular dynamics simulations (J. Chem. Phys. 2013, 139, 214304). The temporal evolution of ionization energies for the excited ππ* state along the QM/MM molecular dynamics trajectories were calculated and are compatible with experimental results, where the two contributions correspond to the relaxation paths in the ππ* state involving different conical intersections with the ground state. Theoretical calculations also show that ionization from the nπ* state is possible at the given photon energies, but we have not found any experimental indication for signal from the nπ* state. In contrast to currently accepted relaxation mechanisms, we suggest that the nπ* state is not involved in the relaxation process of thymine in aqueous solution.

Time-resolved photoelectron spectroscopy at low kinetic energies (≲5 eV) is applied to dilute iodide solutions with different surface and bulk contributions. The results indicate a pronounced surface sensitivity. Signals assigned to solvated electrons near the liquid surface decay rapidly on a sub-ps timescale. In contrast to the literature, a long-lived surface solvated electron at 1.6 eV binding energy is not observed.

Time-resolved photoelectron spectroscopy is applied to study the excited state dynamics of the DNA base adenine and its ribonucleoside adenosine in aqueous solution for pump and probe photon energies in the range between 4.66 eV and 5.21 eV. We follow the evolution of the prepared excited state on the potential energy surface and retrieve lifetimes of the S1 state under different excitation conditions.

Electrokinetic charging of aqueous microjets was characterized by measuring streaming currents as a function of sodium iodide salt concentration. Measured streaming currents at high salt concentrations (up to 0.5 M) varied nonmonotonically with the jet velocity and can be explained by a multipolar charge distribution at the nozzle-water interface. In the case of potassium fluoride no multipolar charge distribution is observed. Electrokinetic potentials were estimated from the streaming currents, under the assumption that all excess charges are confined within the liquid jet. Measured photoelectron spectra indicate much smaller streaming potentials. To resolve the apparent discrepancy, we propose that a significant fraction of excess charges evaporates in the form of ion-water clusters.

We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 μm thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition making femtosecond time-resolved experiments feasible. We describe the experimental setup, a detailed spectrometer characterization based on the spectroscopy of nitric oxide in the gas phase, and results from femtosecond time-resolved experiments on sodium iodide solutions. The latter experiments reveal the formation and evolution of the solvated electron and we characterize two distinct spectral components corresponding to initially thermalized and unthermalized solvated electrons. The absence of dark states in photoionization, the direct measurement of electron binding energies, and the ability to resolve dynamic processes on the femtosecond time scale make time-resolved photoelectron spectroscopy from the liquid jet a very promising method for the characterization of photochemical processes in liquids.

Solvated electrons are among the most reductive species in aqueous environment. Diamond materials have been proposed as a promising source for solvated electrons, but the underlying emission process in water...

Conductive, boron doped diamond (BDD) is an extraordinary material with many applications in electrochemistry due to its wide potential window, outstanding robustness, low capacitance and resistance to fouling. However, in photoelectrochemistry, BDD usually requires UV light for excitation, which impedes e. g., usage in CO2 to fuel reduction. In this work, a heavily boron doped, nanostructured diamond electrode with enhanced light absorption has been developed. It is manufactured from BDD by reactive ion etching and presents a coral‐like structure with pore diameters in the nanometer range, ensuring a huge surface area. The strong light absorbance of this material is clearly visible from its black color. Consequently, the material is called Diamond Black (DB). Electrochemical and X‐ray photoelectron spectroscopy measurements performed at near‐ambient pressure conditions of water vapor demonstrate increased surface reactivity for the hydrogen‐terminated DB compared to oxidized surfaces. Depending on the surface termination, the wettability and hence the electrochemically accessible area can be changed. Photoelectrochemical conversion of CO2 was demonstrated using a Cu2O‐modified electrode in ionic liquids under solar illumination. High formic acid production rates at low catalyst deposition times can be obtained paired with an increased catalyst stability on the DB surface.