Retrieval of Genuine Ultraviolet Liquid-Microjet Photoelectron Spectra

Ultraviolet liquid-microjet photoelectron spectroscopy is a powerful technique for the determination of electron binding energies of molecules in aqueous solution and for exploring their photochemical dynamics. However, our poor understanding of inelastic scattering of low energy electrons (<10 eV) in water has hindered the determination of accurate vertical ionization energies; although several algorithms have been implemented to retrieve genuine binding energies from experimental spectra, a consensus on the parameters employed is yet to be reached. Here, we investigate the effect of these parameters on the retrieval of true photoelectron spectra of water, phenol, and phenolate. We show that the scattering cross sections, obtained by extrapolating the cross sections in amorphous ice to zero electron kinetic energy, describe the distortion observed in our spectra accurately and that the description of the transmission of electrons at the liquid-vacuum interface is crucial to infer a value for the electron affinity of water at the surface, and we emphasize the importance of considering concentration depth profiles when retrieving true photoelectron spectra of surface-active solutes. Our work highlights the potential for accurate ultraviolet photoelectron spectroscopy of aqueous solutions of organic molecules.