Photoelectron spectrum and breakdown diagram of ethanolamine: conformers, excited states, and thermochemistry.

Advanced theoretical methodologies and photoelectron photoion coincidence spectroscopy were used to investigate the photoionization of ethanolamine in the 8-18 eV energy range. We identified the low-lying cation conformers and the excited cation electronic states after vertical excitation from the most stable neutral conformer computationally. The TPES is composed of broad, structureless bands because of unfavorable Franck-Condon factors for origin transitions upon ionization, populating the D-D cationic states from the most stable neutral conformer, g'Gg'.

Cyclopentene and cyclopentadiene formation in isoprene pyrolysis.

Photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) was used to identify the isoprene pyrolysis products in a SiC microreactor at 1400 °C with the help of literature and Franck-Condon simulated reference spectra for molecular species at the detected / ratios. The key observation is the presence of equimolar amounts of isoprene and cyclopentene at the pyrolysis temperature based on the / 68 ms-TPES, indicating kinetically allowed isoprene isomerization concurrently with fragmentation reactions. This isomerization was computationally explored and was found to take place a short-lived vinylcyclopropane intermediate, which was previously proposed to isomerize into isoprene and cyclopentene, with the latter product being dominant.

Catalytic pyrolysis mechanism of lignin moieties driven by aldehyde, hydroxyl, methoxy, and allyl functionalization: the role of reactive quinone methide and ketene intermediates.

The catalytic pyrolysis of guaiacol-based lignin monomers, vanillin, syringol, and eugenol over commercial HZSM-5 has been investigated using Photoelectron Photoion Coincidence (PEPICO) spectroscopy to unveil the reaction mechanism by detecting reactive intermediates, such as quinone methides and ketenes, and products. shares the decomposition mechanism with guaiacol due to prompt and efficient decarbonylation, which allows us to control this reaction leading to a phenol selectivity increase by switching to a faujasite catalyst and decreasing the Si/Al ratio. first demethylates to 3-methoxycatechol, which mainly dehydroxylates to - and -guaiacol.

A solution for 4-propylguaiacol hydrodeoxygenation without ring saturation.

We investigate solvent effects in the hydrodeoxygenation of 4-propylguaiacol (4PG, 166 amu), a key lignin-derived monomer, over Ru/C catalyst by combined operando synchrotron photoelectron photoion coincidence (PEPICO) spectroscopy and molecular dynamics simulations. With and without isooctane co-feeding, ring-hydrogenated 2-methoxy-4-propylcyclohexanol (172 amu) is the first product, due to the favorable flat adsorption configuration of 4PG on the catalyst surface. In contrast, tetrahydrofuran (THF)-a polar aprotic solvent that is representative of those used for lignin solubilization and upgrading-strongly coordinates to the catalyst surface at the oxygen atom.

VUV absorption spectra of water and nitrous oxide by a double-duty differentially pumped gas filter.

The differentially pumped rare-gas filter at the end of the VUV beamline of the Swiss Light Source has been adapted to house a windowless absorption cell for gases. Absorption spectra can be recorded from 7 eV to up to 21 eV photon energies routinely, as shown by a new water and nitrous oxide absorption spectrum. By and large, the spectra agree with previously published ones both in terms of resonance energies and absorption cross sections, but that of NO exhibits a small shift in the {\tilde{\bf D}} band and tentative fine structures that have not yet been fully described.