Séminaire CulturChem | Gustavo Garcia-Macias "Application of photoelectron spectroscopy for product electron in gas phase chemistry"

Dans le cadre des séminaires CulturChem de l'ED406

Gustavo GARCIA-MACIAS (SOLEIL Synchrotron)

Présentera un séminaire intitulé

"Applications of photoelectron spectroscopy for product detection in gas phase chemistry"

Full detection of all products and intermediates involved at any given time on a chemical reaction is considered as the ultimate goal, leading to a complete description of the reaction mechanism and therefore to its control. Optical methods, although very sensitive, lack the required universality needed for complex determinations. Because every species can be ionised, mass spectrometry also appears as a method of choice, however extensive fragmentation due to the high energy ionisation sources in commercial spectrometers, and the inability to differentiate structural isomers limit its usability. In the past decade, several groups have combined mass spectrometry with VUV tuneable sources to minimise fragmentation by ionising close to the first threshold (soft ionization), and to record the photoion efficiency (PIE) curves as a function of photon energy, which provide
structural information, as demonstrated in complex systems such as low-pressure flames.

Because the structural information contained in the PIEs is limited, a more recent development that increases sensitivity and isomer differentiation will be discussed here based on coupling photoelectron spectroscopy to photoion mass spectrometry. Although photoelectron-photoion coincidence (PEPICO) techniques have been applied extensively to acquire detailed knowledge on photoionisation processes since the early seventies, it is only recently that are being applied for advanced product detection in complex gas phase media. I will present examples of application of modern double imaging PEPICO (i2PEPICO) techniques in combination with tuneable VUV synchrotron radiation for the study of complex systems of environmental interest such as combustion, secondary organic aerosol formation5 or atmospheric oxidation. I will also present a novel method to measure circular dischroism in the gas phase that can also be coupled to mass spectrometry for online enantioselective analysis on products or reactive intermediates, as I will show in the case of pepper oil analysis.