Photoelectron spectroscopy of liquid water, some alcohols, and pure nonane in free micro jets

Abstract

The recently developed technique of accessing volatile liquids in a high vacuum environment by using a very thin liquid jet is implemented to carry out the first measurements of photoelectron spectra of pure liquid water, methanol, ethanol, 1-propanol, 1-butanol, and benzyl alcohol as well as of liquid n-nonane. The apparatus, which consists of a commercial hemispherical (10 cm mean radius) electron analyzer and a hollow cathode discharge He I light source is described in detail and the problems of the sampling of the photoelectrons in such an environment are discussed. For water and most of the alcohols up to six different electronic bands could be resolved. The spectra of 1-butanol and n-nonane show two weakly discernable peaks from which the threshold ionization potential could be determined. A deconvolution of the photoelectron spectra is used to extract ionization potentials of individual molecular bands of molecules near the surface of the liquid and shifts of the order of 1 eV compared to the gas phase are observed. A molecular orientation for water molecules at the surface of liquid water is inferred from a comparison of the relative band strengths with the gas phase. Similar effects are also observed for some of the alcohols. The results are discussed in terms of a simple “Born-solvation” model.

Ultrafast electronic spectroscopy for chemical analysis near liquid water interfaces: concepts and applications

“…In addition to the element specificity, the technique can also provide information about an element's chemical environment or oxidation state. Due to the technical and conceptual problems with (volatile) liquids in vacuum, liquid phase (high pressure) ESCA is much less well established [3][4][5][6][7][8] than XPS at solid state surfaces. Only after Faubel et al developed the liquid beam technique in vacuum also volatile liquids like water could be investigated with photoelectron spectroscopy in vacuum [5][6][7][8].…”

“…Due to the technical and conceptual problems with (volatile) liquids in vacuum, liquid phase (high pressure) ESCA is much less well established [3][4][5][6][7][8] than XPS at solid state surfaces. Only after Faubel et al developed the liquid beam technique in vacuum also volatile liquids like water could be investigated with photoelectron spectroscopy in vacuum [5][6][7][8]. Since then, the chemical shift in the static ESCA approach has also been a particularly powerful observable for probing electron densities and molecular orbital energies in different liquid molecular environments [9,10].…”

“…15. As visible for negative delay times the EUV probe beam alone in the experiment ionizes water and produces photoelectrons from the 1 b 1 , 3 a 1 , 1 b 2 , and 2 a 1 valence electrons of liquid water and some residual gas phase water [5,8]. The photoelectron spectrum of water is well known and prominent features for the valence electrons are easily assignable to the 1 b 1 , 3 a 1 , 1 b 2 orbitals (for assignments and features of orbitals of water see Fig.…”

“…6). The target is a liquid microjet, which was introduced by Faubel [5][6][7][8] some time ago (Fig. 4).…”

Hydrogen bond dynamics of superheated water and methanol by ultrafast IR-pump and EUV-photoelectron probe spectroscopy

“…The assignment of the photoemission lines (5a 0 , 1a 00 , 6a 0 , 7a 0 , and 2a 00 ) has been taken from ref. 76. Beyond the 2a 00 gas phase photoelectron emission line towards lower binding energies a liquid band 2a 00 liq is observed.…”