AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Probing Structure and Chemical Properties of Free-standing Clusters with Synchrotron Radiation
NONNE PRISLE, J. Malila, K. Jänkälä, M. Patanen, M. Huttula, University of Oulu, Oulu, Finland
Abstract Number: 775 Working Group: Instrumentation and Methods
Abstract Despite intensive laboratory and field measurements, dating back over a century ago, molecular details of formation and growth of new atmospheric particles remain elusive. Changes in new particle formation and growth rates can affect global concentrations of cloud condensation nuclei, thus contributing to anthropogenic radiative forcing (Merikanto et al., Atmos. Chem. Phys., 8601, 2009). A mechanistic understanding of these processes, including phase and surface properties of newly formed particles, is therefore vital for reducing uncertainties in climate forecasts. Deductions based on indirect measurements have proven inconclusive (Kupiainen-Määttä et al., J. Aerosol Sci., 127, 2014), and recently there has been a surge towards measurements setups yielding molecular-level resolution of cluster properties.
Surfaces are moving into the spotlight of the atmospheric aerosol community. A suite of novel instrumentation developments now allow for highly surface sensitive chemical characterization of systems with increasing resemblance to atmospheric aerosols. The Multiuse Setup for Clusters Emission (MUSCLE) is custom-built for producing freestanding multicomponent nanoparticles with well-defined composition, and directly characterizing their chemical, structural, and phase-state properties using synchrotron radiation based spectroscopy at the FinEstBeAMS beamline, MAX IV Laboratory. The brightness of the new MAX IV synchrotron light source enables the use of powerful surface sensitive photoelectron spectroscopy for low density samples, in particular freestanding cluster beams of atmospherically relevant trace components.
MUSCLE is our next generation cluster source based on the proven basic design of the Exchange Metal Cluster (EXMEC) source (Huttula et al., J. Electron Spectroscopy and Related Phenomena, 145, 2010). Using this setup, we have generated clusters of e.g. aqueous alkali halides with controlled composition (Hautala et al., Phys. Rev. B, 45402, 2016) and semi-volatile atmospheric organics, including stearic acid (unpublished data). With synchrotron based photoelectron spectroscopy we have e.g. observed size-dependent structural phase transitions for CsBr clusters (Hautala et al., 2016).