The Multiphase Chemistry Group in the Laboratory of Atmospheric Chemistry (LAC) looks back to a nearly 20 years record of activities with in situ X-ray photoelectron spectroscopy (XPS) and in situ scanning transmission X-ray spectromicroscopy (STXM) to address key fundamental questions in atmospheric chemistry. This is the time to consider new horizons, align with current and future needs in atmospheric sciences, and to identify novel opportunities driven by upcoming trends in methods, technologies and facilities. This has been the topic of the Workshop ‘X-ray and Neutron Spectroscopy, Scattering and Imaging in Atmospheric Chemistry’, held at PSI 13 – 15 November 2024.
The aim of the workshop was to foster new directions in atmospheric chemistry research at large-scale facilities like the Swiss Light Source (SLS), the Swiss Spallation Neutron Source (SINQ), and the Free Electron Laser (SwissFel) at PSI to address questions related to Earth’s atmosphere. Using techniques such as spectroscopy, scattering and imaging, structures and processes at the molecular and atomic level are investigated to understand their connection to macroscopic physical properties and chemical reactivity. With this workshop, we brought together international scientific pioneers and drivers in developing novel techniques at large-scale facilities with the leading scientists in atmospheric research of LAC and their collaborators to identify novel research avenues related to societally highly relevant topics such as climate change and air pollution.
Recent developments at large-scale facilities that open up new science possibilities for atmospheric research set one part of the topics. Among these are investigations of nanometer-sized droplets and particles, time-resolved measurements to track chemistry and structural changes on the picosecond time scale, highly resolved depth profiles at the interface in the nm range, and probing deeper layers in complex samples, investigating charge distribution at interfaces, working with sensitive samples, and combining simultaneous use of several methods on the same sample. These developments have been ongoing in spectroscopy, scattering, and in imaging. Experts in these fields met at PSI to discuss how the advancing techniques can be used in complementary ways. The scientific context was given by linking to current key questions in atmospheric science among which are the chemistry in constrained and highly concentrated environments, the role of delicate biomolecules and surfactants, the role of charged interfaces as a driver of redox chemistry, fundamental understanding of the hydrogen bonding network in highly concentrated water containing media, and ice nucleation.
The workshop was held in a format allowing extensive discussion of each input presentation by both emerging and senior scientists of these two research communities that met for the first time. On the technical side, the discussions circled around sample environments compatible with different experimental boundary conditions, the relative benefits of methods probing single particle versus aerosol ensembles, increasing the depth resolution of methods accessing the condensed phase – gas interface, or the role of beam damage. Furthermore, the demand for the combination of scattering and spectroscopy and for hosting experimental setups in a consistent way at different facilities was discussed. On the scientific side, an overarching topic was the bridging between the molecular level focus of individual studies and the large scale atmospheric processes active in determining chemical composition and climate.
Contact
Markus Ammann, Thorsten Bartels-Rausch, Claudia Mohr
Laboratory of Atmospheric Chemistry
Paul Scherrer Institute PSI, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 4049
E-mail: markus.ammann@psi.ch